[bpt/emacs.git] / lisp / calendar / calendar.el

;;; calendar.el --- calendar functions

;; Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1997,
;;	2000, 2001, 2003, 2004 Free Software Foundation, Inc.

;; Author: Edward M. Reingold <reingold@cs.uiuc.edu>
;; Keywords: calendar
;; Human-Keywords: calendar, Gregorian calendar, diary, holidays

;; This file is part of GNU Emacs.

;; GNU Emacs is free software; you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation; either version 2, or (at your option)
;; any later version.

;; GNU Emacs is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;; GNU General Public License for more details.

;; You should have received a copy of the GNU General Public License
;; along with GNU Emacs; see the file COPYING.  If not, write to the
;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
;; Boston, MA 02111-1307, USA.

;;; Commentary:

;; This collection of functions implements a calendar window.  It
;; generates a calendar for the current month, together with the
;; previous and coming months, or for any other three-month period.
;; The calendar can be scrolled forward and backward in the window to
;; show months in the past or future; the cursor can move forward and
;; backward by days, weeks, or months, making it possible, for
;; instance, to jump to the date a specified number of days, weeks, or
;; months from the date under the cursor.  The user can display a list
;; of holidays and other notable days for the period shown; the
;; notable days can be marked on the calendar, if desired.  The user
;; can also specify that dates having corresponding diary entries (in
;; a file that the user specifies) be marked; the diary entries for
;; any date can be viewed in a separate window.  The diary and the
;; notable days can be viewed independently of the calendar.  Dates
;; can be translated from the (usual) Gregorian calendar to the day of
;; the year/days remaining in year, to the ISO commercial calendar, to
;; the Julian (old style) calendar, to the Hebrew calendar, to the
;; Islamic calendar, to the Baha'i calendar, to the French
;; Revolutionary calendar, to the Mayan calendar, to the Chinese
;; calendar, to the Coptic calendar, to the Ethiopic calendar, and to
;; the astronomical (Julian) day number.  When floating point is
;; available, times of sunrise/sunset can be displayed, as can the
;; phases of the moon.  Appointment notification for diary entries is
;; available.  Calendar printing via LaTeX is available.

;; The following files are part of the calendar/diary code:

;;       appt.el                       Appointment notification
;;       cal-china.el                  Chinese calendar
;;       cal-coptic.el                 Coptic/Ethiopic calendars
;;       cal-dst.el                    Daylight savings time rules
;;       cal-hebrew.el                 Hebrew calendar
;;       cal-islam.el                  Islamic calendar
;;       cal-bahai.el                  Baha'i calendar
;;       cal-iso.el                    ISO calendar
;;       cal-julian.el                 Julian/astronomical calendars
;;       cal-mayan.el                  Mayan calendars
;;       cal-menu.el                   Menu support
;;       cal-move.el                   Movement in the calendar
;;       cal-persia.el                 Persian calendar
;;       cal-tex.el                    Calendars in LaTeX
;;       cal-x.el                      X-windows dedicated frame functions
;;       diary-lib.el                  Diary functions
;;       holidays.el                   Holiday functions
;;       lunar.el                      Phases of the moon
;;       solar.el                      Sunrise/sunset, equinoxes/solstices

;; Technical details of all the calendrical calculations can be found in
;; ``Calendrical Calculations'' by Nachum Dershowitz and Edward M. Reingold,
;; Cambridge University Press (1997).

;; An earlier version of the technical details appeared in
;; ``Calendrical Calculations'' by Nachum Dershowitz and Edward M. Reingold,
;; Software--Practice and Experience, Volume 20, Number 9 (September, 1990),
;; pages 899-928.  ``Calendrical Calculations, Part II: Three Historical
;; Calendars'' by E. M. Reingold,  N. Dershowitz, and S. M. Clamen,
;; Software--Practice and Experience, Volume 23, Number 4 (April, 1993),
;; pages 383-404.

;; Hard copies of these two papers can be obtained by sending email to
;; reingold@cs.uiuc.edu with the SUBJECT "send-paper-cal" (no quotes) and
;; the message BODY containing your mailing address (snail).

;; Comments, corrections, and improvements should be sent to
;;  Edward M. Reingold               Department of Computer Science
;;  (217) 333-6733                   University of Illinois at Urbana-Champaign
;;  reingold@cs.uiuc.edu             1304 West Springfield Avenue
;;                                   Urbana, Illinois 61801

;;; Code:

(eval-when-compile
  (defvar displayed-month)
  (defvar displayed-year)
  (defvar calendar-month-name-array)
  (defvar calendar-starred-day))

(defun calendar-version ()
  (interactive)
  (message "Version 6, October 12, 1995"))

(defgroup calendar nil
  "Calendar and time management support."
  :group 'applications)

(defgroup diary nil
  "Emacs diary."
  :group 'calendar)

(defgroup appt nil
  "Appointment notification."
  :group 'calendar)

(defgroup holidays nil
  "Holidays support in calendar."
  :group 'calendar
  :prefix "calendar-"
  :group 'local)

(defgroup chinese-calendar nil
  "Chinese calendar support."
  :group 'calendar)

(defgroup calendar-tex nil
  "Options for printing calendar with LaTeX."
  :prefix "cal-tex-"
  :group 'calendar)

(defgroup calendar-hooks nil
  "Calendar hooks."
  :prefix "calendar-"
  :group 'calendar)


;;;###autoload
(defcustom calendar-week-start-day 0
  "*The day of the week on which a week in the calendar begins.
0 means Sunday (default), 1 means Monday, and so on."
  :type 'integer
  :group 'calendar)

;;;###autoload
(defcustom calendar-offset 0
  "*The offset of the principal month from the center of the calendar window.
0 means the principal month is in the center (default), -1 means on the left,
+1 means on the right.  Larger (or smaller) values push the principal month off
the screen."
  :type 'integer
  :group 'calendar)

;;;###autoload
(defcustom view-diary-entries-initially nil
  "*Non-nil means display current date's diary entries on entry to calendar.
The diary is displayed in another window when the calendar is first displayed,
if the current date is visible.  The number of days of diary entries displayed
is governed by the variable `number-of-diary-entries'.  This variable can
be overridden by the value of `calendar-setup'."
  :type 'boolean
  :group 'diary)

;;;###autoload
(defcustom number-of-diary-entries 1
  "*Specifies how many days of diary entries are to be displayed initially.
This variable affects the diary display when the command \\[diary] is used,
or if the value of the variable `view-diary-entries-initially' is t.  For
example, if the default value 1 is used, then only the current day's diary
entries will be displayed.  If the value 2 is used, then both the current
day's and the next day's entries will be displayed.

The value can also be a vector such as [0 2 2 2 2 4 1]; this value
says to display no diary entries on Sunday, the display the entries
for the current date and the day after on Monday through Thursday,
display Friday through Monday's entries on Friday, and display only
Saturday's entries on Saturday.

This variable does not affect the diary display with the `d' command
from the calendar; in that case, the prefix argument controls the
number of days of diary entries displayed."
  :type '(choice (integer :tag "Entries")
		 (vector :value [0 0 0 0 0 0 0]
			 (integer :tag "Sunday")
			 (integer :tag "Monday")
			 (integer :tag "Tuesday")
			 (integer :tag "Wednesday")
			 (integer :tag "Thursday")
			 (integer :tag "Friday")
			 (integer :tag "Saturday")))
  :group 'diary)

;;;###autoload
(defcustom mark-diary-entries-in-calendar nil
  "*Non-nil means mark dates with diary entries, in the calendar window.
The marking symbol is specified by the variable `diary-entry-marker'."
  :type 'boolean
  :group 'diary)

;;;###autoload
(defcustom calendar-remove-frame-by-deleting nil
  "*Determine how the calendar mode removes a frame no longer needed.
If nil, make an icon of the frame.  If non-nil, delete the frame."
  :type 'boolean
  :group 'view)

(defvar diary-face 'diary-face
  "Face name to use for diary entries.")
(defface diary-face
  '((((class color) (background light))
     :foreground "red")
    (((class color) (background dark))
     :foreground "yellow")
    (t
     :weight bold))
  "Face for highlighting diary entries."
  :group 'diary)

(defface calendar-today-face
  '((t (:underline t)))
  "Face for indicating today's date."
  :group 'diary)

(defface holiday-face
  '((((class color) (background light))
     :background "pink")
    (((class color) (background dark))
     :background "chocolate4")
    (t
     :inverse-video t))
  "Face for indicating dates that have holidays."
  :group 'diary)

(eval-after-load "facemenu"
  '(progn
     (add-to-list 'facemenu-unlisted-faces 'diary-face)
     (add-to-list 'facemenu-unlisted-faces 'calendar-today-face)
     (add-to-list 'facemenu-unlisted-faces 'holiday-face)))

(defcustom diary-entry-marker
  (if (not (display-color-p))
      "+"
    'diary-face)
  "*How to mark dates that have diary entries.
The value can be either a single-character string or a face."
  :type '(choice string face)
  :group 'diary)

(defcustom calendar-today-marker
  (if (not (display-color-p))
      "="
    'calendar-today-face)
  "*How to mark today's date in the calendar.
The value can be either a single-character string or a face.
Marking today's date is done only if you set up `today-visible-calendar-hook'
to request that."
  :type '(choice string face)
  :group 'calendar)

(defcustom calendar-holiday-marker
  (if (not (display-color-p))
      "*"
    'holiday-face)
  "*How to mark notable dates in the calendar.
The value can be either a single-character string or a face."
  :type '(choice string face)
  :group 'calendar)

;;;###autoload
(defcustom view-calendar-holidays-initially nil
  "*Non-nil means display holidays for current three month period on entry.
The holidays are displayed in another window when the calendar is first
displayed."
  :type 'boolean
  :group 'holidays)

;;;###autoload
(defcustom mark-holidays-in-calendar nil
  "*Non-nil means mark dates of holidays in the calendar window.
The marking symbol is specified by the variable `calendar-holiday-marker'."
  :type 'boolean
  :group 'holidays)

;;;###autoload
(defcustom all-hebrew-calendar-holidays nil
  "*If nil, show only major holidays from the Hebrew calendar.
This means only those Jewish holidays that appear on secular calendars.

If t, show all the holidays that would appear in a complete Hebrew calendar."
  :type 'boolean
  :group 'holidays)

;;;###autoload
(defcustom all-christian-calendar-holidays nil
  "*If nil, show only major holidays from the Christian calendar.
This means only those Christian holidays that appear on secular calendars.

If t, show all the holidays that would appear in a complete Christian
calendar."
  :type 'boolean
  :group 'holidays)

;;;###autoload
(defcustom all-islamic-calendar-holidays nil
  "*If nil, show only major holidays from the Islamic calendar.
This means only those Islamic holidays that appear on secular calendars.

If t, show all the holidays that would appear in a complete Islamic
calendar."
  :type 'boolean
  :group 'holidays)

(defcustom diary-file-name-prefix-function (function (lambda (str) str))
  "*The function that will take a diary file name and return the desired prefix."
  :type 'function
  :group 'diary)

;;;###autoload
(defcustom all-bahai-calendar-holidays nil
  "*If nil, show only major holidays from the Baha'i calendar.
These are the days on which work and school must be suspended.

If t, show all the holidays that would appear in a complete Baha'i
calendar."
  :type 'boolean
  :group 'holidays)

;;;###autoload
(defcustom calendar-load-hook nil
  "*List of functions to be called after the calendar is first loaded.
This is the place to add key bindings to `calendar-mode-map'."
  :type 'hook
  :group 'calendar-hooks)

;;;###autoload
(defcustom initial-calendar-window-hook nil
  "*List of functions to be called when the calendar window is first opened.
The functions invoked are called after the calendar window is opened, but
once opened is never called again.  Leaving the calendar with the `q' command
and reentering it will cause these functions to be called again."
  :type 'hook
  :group 'calendar-hooks)

;;;###autoload
(defcustom today-visible-calendar-hook nil
  "*List of functions called whenever the current date is visible.
This can be used, for example, to replace today's date with asterisks; a
function `calendar-star-date' is included for this purpose:
    (setq today-visible-calendar-hook 'calendar-star-date)
It can also be used to mark the current date with `calendar-today-marker';
a function is also provided for this:
    (setq today-visible-calendar-hook 'calendar-mark-today)

The corresponding variable `today-invisible-calendar-hook' is the list of
functions called when the calendar function was called when the current
date is not visible in the window.

Other than the use of the provided functions, the changing of any
characters in the calendar buffer by the hooks may cause the failure of the
functions that move by days and weeks."
  :type 'hook
  :group 'calendar-hooks)

;;;###autoload
(defcustom today-invisible-calendar-hook nil
  "*List of functions called whenever the current date is not visible.

The corresponding variable `today-visible-calendar-hook' is the list of
functions called when the calendar function was called when the current
date is visible in the window.

Other than the use of the provided functions, the changing of any
characters in the calendar buffer by the hooks may cause the failure of the
functions that move by days and weeks."
  :type 'hook
  :group 'calendar-hooks)

;;;###autoload
(defcustom calendar-move-hook nil
  "*List of functions called whenever the cursor moves in the calendar.

For example,

  (add-hook 'calendar-move-hook (lambda () (view-diary-entries 1)))

redisplays the diary for whatever date the cursor is moved to."
  :type 'hook
  :group 'calendar-hooks)

;;;###autoload
(defcustom diary-file "~/diary"
  "*Name of the file in which one's personal diary of dates is kept.

The file's entries are lines beginning with any of the forms
specified by the variable `american-date-diary-pattern', by default:

            MONTH/DAY
            MONTH/DAY/YEAR
            MONTHNAME DAY
            MONTHNAME DAY, YEAR
            DAYNAME

with the remainder of the line being the diary entry string for
that date.  MONTH and DAY are one or two digit numbers, YEAR is a
number and may be written in full or abbreviated to the final two
digits (if `abbreviated-calendar-year' is non-nil).  MONTHNAME
and DAYNAME can be spelled in full (as specified by the variables
`calendar-month-name-array' and `calendar-day-name-array'),
abbreviated (as specified by `calendar-month-abbrev-array' and
`calendar-day-abbrev-array') with or without a period,
capitalized or not.  Any of DAY, MONTH, or MONTHNAME, YEAR can be
`*' which matches any day, month, or year, respectively. If the
date does not contain a year, it is generic and applies to any
year.  A DAYNAME entry applies to the appropriate day of the week
in every week.

The European style (in which the day precedes the month) can be
used instead, if you execute `european-calendar' when in the
calendar, or set `european-calendar-style' to t in your .emacs
file.  The European forms (see `european-date-diary-pattern') are

            DAY/MONTH
            DAY/MONTH/YEAR
            DAY MONTHNAME
            DAY MONTHNAME YEAR
            DAYNAME

To revert to the default American style from the European style, execute
`american-calendar' in the calendar.

A diary entry can be preceded by the character
`diary-nonmarking-symbol' (ordinarily `&') to make that entry
nonmarking--that is, it will not be marked on dates in the calendar
window but will appear in a diary window.

Multiline diary entries are made by indenting lines after the first with
either a TAB or one or more spaces.

Lines not in one the above formats are ignored.  Here are some sample diary
entries (in the default American style):

     12/22/1988 Twentieth wedding anniversary!!
     &1/1. Happy New Year!
     10/22 Ruth's birthday.
     21: Payday
     Tuesday--weekly meeting with grad students at 10am
              Supowit, Shen, Bitner, and Kapoor to attend.
     1/13/89 Friday the thirteenth!!
     &thu 4pm squash game with Lloyd.
     mar 16 Dad's birthday
     April 15, 1989 Income tax due.
     &* 15 time cards due.

If the first line of a diary entry consists only of the date or day name with
no trailing blanks or punctuation, then that line is not displayed in the
diary window; only the continuation lines is shown.  For example, the
single diary entry

     02/11/1989
      Bill Blattner visits Princeton today
      2pm Cognitive Studies Committee meeting
      2:30-5:30 Lizzie at Lawrenceville for `Group Initiative'
      4:00pm Jamie Tappenden
      7:30pm Dinner at George and Ed's for Alan Ryan
      7:30-10:00pm dance at Stewart Country Day School

will appear in the diary window without the date line at the beginning.  This
facility allows the diary window to look neater, but can cause confusion if
used with more than one day's entries displayed.

Diary entries can be based on Lisp sexps.  For example, the diary entry

      %%(diary-block 11 1 1990 11 10 1990) Vacation

causes the diary entry \"Vacation\" to appear from November 1 through
November 10, 1990.  Other functions available are `diary-float',
`diary-anniversary', `diary-cyclic', `diary-day-of-year',
`diary-iso-date', `diary-french-date', `diary-hebrew-date',
`diary-islamic-date', `diary-bahai-date', `diary-mayan-date',
`diary-chinese-date', `diary-coptic-date', `diary-ethiopic-date',
`diary-persian-date', `diary-yahrzeit', `diary-sunrise-sunset',
`diary-phases-of-moon', `diary-parasha', `diary-omer',
`diary-rosh-hodesh', and `diary-sabbath-candles'.  See the
documentation for the function `list-sexp-diary-entries' for more
details.

Diary entries based on the Hebrew, the Islamic and/or the Baha'i
calendar are also possible, but because these are somewhat slow, they
are ignored unless you set the `nongregorian-diary-listing-hook' and
the `nongregorian-diary-marking-hook' appropriately.  See the
documentation for these functions for details.

Diary files can contain directives to include the contents of other files; for
details, see the documentation for the variable `list-diary-entries-hook'."
  :type 'file
  :group 'diary)

;;;###autoload
(defcustom diary-nonmarking-symbol "&"
  "*Symbol indicating that a diary entry is not to be marked in the calendar."
  :type 'string
  :group 'diary)

;;;###autoload
(defcustom hebrew-diary-entry-symbol "H"
  "*Symbol indicating a diary entry according to the Hebrew calendar."
  :type 'string
  :group 'diary)

;;;###autoload
(defcustom islamic-diary-entry-symbol "I"
  "*Symbol indicating a diary entry according to the Islamic calendar."
  :type 'string
  :group 'diary)

;;;###autoload
(defcustom bahai-diary-entry-symbol "B"
  "*Symbol indicating a diary entry according to the Baha'i calendar."
  :type 'string
  :group 'diary)

;;;###autoload
(defcustom diary-include-string "#include"
  "*The string indicating inclusion of another file of diary entries.
See the documentation for the function `include-other-diary-files'."
  :type 'string
  :group 'diary)

(defcustom diary-glob-file-regexp-prefix "^\\#"
  "*The regular expression that gets pre-pended to each of the attribute-regexp's for file-wide specifiers."
  :type 'regexp
  :group 'diary)

(defcustom diary-face-attrs
  '((" *\\[foreground:\\([-a-z]+\\)\\]$" 1 :foreground string)
    (" *\\[background:\\([-a-z]+\\)\\]$" 1 :background string)
    (" *\\[width:\\([-a-z]+\\)\\]$" 1 :width symbol)
    (" *\\[height:\\([-0-9a-z]+\\)\\]$" 1 :height int)
    (" *\\[weight:\\([-a-z]+\\)\\]$" 1 :weight symbol)
    (" *\\[slant:\\([-a-z]+\\)\\]$" 1 :slant symbol)
    (" *\\[underline:\\([-a-z]+\\)\\]$" 1 :underline stringtnil)
    (" *\\[overline:\\([-a-z]+\\)\\]$" 1 :overline stringtnil)
    (" *\\[strike-through:\\([-a-z]+\\)\\]$" 1 :strike-through stringtnil)
    (" *\\[inverse-video:\\([-a-z]+\\)\\]$" 1 :inverse-video tnil)
    (" *\\[face:\\([-0-9a-z]+\\)\\]$" 1 :face string)
    (" *\\[font:\\([-a-z0-9]+\\)\\]$" 1 :font string)
    ;; Unsupported.
;;;    (" *\\[box:\\([-a-z]+\\)\\]$" 1 :box)
;;;    (" *\\[stipple:\\([-a-z]+\\)\\]$" 1 :stipple)
    )
  "*A list of (regexp regnum attr attrtype) lists where the
regexp says how to find the tag, the regnum says which
parenthetical sub-regexp this regexp looks for, and the attr says
which attribute of the face (or that this _is_ a face) is being
modified."
  :type 'sexp
  :group 'diary)

(defcustom diary-file-name-prefix nil
  "If non-nil each diary entry is prefixed with the name of the file where it is defined."
  :type 'boolean
  :group 'diary)

;;;###autoload
(defcustom sexp-diary-entry-symbol "%%"
  "*The string used to indicate a sexp diary entry in `diary-file'.
See the documentation for the function `list-sexp-diary-entries'."
  :type 'string
  :group 'diary)

;;;###autoload
(defcustom abbreviated-calendar-year t
  "*Interpret a two-digit year DD in a diary entry as either 19DD or 20DD.
For the Gregorian calendar; similarly for the Hebrew, Islamic and
Baha'i calendars.  If this variable is nil, years must be written in
full."
  :type 'boolean
  :group 'diary)

;;;###autoload
(defcustom european-calendar-style nil
  "*Use the European style of dates in the diary and in any displays.
If this variable is t, a date 1/2/1990 would be interpreted as February 1,
1990.  The default European date styles (see `european-date-diary-pattern')
are

            DAY/MONTH
            DAY/MONTH/YEAR
            DAY MONTHNAME
            DAY MONTHNAME YEAR
            DAYNAME

Names can be capitalized or not, written in full (as specified by the
variable `calendar-day-name-array'), or abbreviated (as specified by
`calendar-day-abbrev-array') with or without a period.  To take effect,
this variable should be set before the calendar package and its associates
are loaded.  Otherwise, use one of the functions `european-calendar' or
`american-calendar' to force the appropriate update."
  :type 'boolean
  :group 'diary)

;;;###autoload
(defcustom american-date-diary-pattern
  '((month "/" day "[^/0-9]")
    (month "/" day "/" year "[^0-9]")
    (monthname " *" day "[^,0-9]")
    (monthname " *" day ", *" year "[^0-9]")
    (dayname "\\W"))
  "*List of pseudo-patterns describing the American patterns of date used.
See the documentation of `diary-date-forms' for an explanation."
  :type '(repeat (choice (cons :tag "Backup"
			       :value (backup . nil)
			       (const backup)
			       (repeat (list :inline t :format "%v"
					     (symbol :tag "Keyword")
					     (choice symbol regexp))))
			 (repeat (list :inline t :format "%v"
				       (symbol :tag "Keyword")
				       (choice symbol regexp)))))
  :group 'diary)

;;;###autoload
(defcustom european-date-diary-pattern
  '((day "/" month "[^/0-9]")
    (day "/" month "/" year "[^0-9]")
    (backup day " *" monthname "\\W+\\<\\([^*0-9]\\|\\([0-9]+[:aApP]\\)\\)")
    (day " *" monthname " *" year "[^0-9]")
    (dayname "\\W"))
  "*List of pseudo-patterns describing the European patterns of date used.
See the documentation of `diary-date-forms' for an explanation."
  :type '(repeat (choice (cons :tag "Backup"
			       :value (backup . nil)
			       (const backup)
			       (repeat (list :inline t :format "%v"
					     (symbol :tag "Keyword")
					     (choice symbol regexp))))
			 (repeat (list :inline t :format "%v"
				       (symbol :tag "Keyword")
				       (choice symbol regexp)))))
  :group 'diary)

(defcustom diary-date-forms
  (if european-calendar-style
      european-date-diary-pattern
    american-date-diary-pattern)
  "*List of pseudo-patterns describing the forms of date used in the diary.
The patterns on the list must be MUTUALLY EXCLUSIVE and should not match
any portion of the diary entry itself, just the date component.

A pseudo-pattern is a list of regular expressions and the keywords `month',
`day', `year', `monthname', and `dayname'.  The keyword `monthname' will
match the name of the month (see `calendar-month-name-array'), capitalized
or not, or its user-specified abbreviation (see `calendar-month-abbrev-array'),
followed by a period or not; it will also match `*'.  Similarly, `dayname'
will match the name of the day (see `calendar-day-name-array'), capitalized or
not, or its user-specified abbreviation (see `calendar-day-abbrev-array'),
followed by a period or not.  The keywords `month', `day', and `year' will
match those numerical values, preceded by arbitrarily many zeros; they will
also match `*'.

The matching of the diary entries with the date forms is done with the
standard syntax table from Fundamental mode, but with the `*' changed so
that it is a word constituent.

If, to be mutually exclusive, a pseudo-pattern must match a portion of the
diary entry itself, the first element of the pattern MUST be `backup'.  This
directive causes the date recognizer to back up to the beginning of the
current word of the diary entry, so in no case can the pattern match more than
a portion of the first word of the diary entry."
  :type '(repeat (choice (cons :tag "Backup"
			       :value (backup . nil)
			       (const backup)
			       (repeat (list :inline t :format "%v"
					     (symbol :tag "Keyword")
					     (choice symbol regexp))))
			 (repeat (list :inline t :format "%v"
				       (symbol :tag "Keyword")
				       (choice symbol regexp)))))
  :group 'diary)

;;;###autoload
(defcustom european-calendar-display-form
  '((if dayname (concat dayname ", ")) day " " monthname " " year)
  "*Pseudo-pattern governing the way a date appears in the European style.
See the documentation of `calendar-date-display-form' for an explanation."
  :type 'sexp
  :group 'calendar)

;;;###autoload
(defcustom american-calendar-display-form
  '((if dayname (concat dayname ", ")) monthname " " day ", " year)
  "*Pseudo-pattern governing the way a date appears in the American style.
See the documentation of `calendar-date-display-form' for an explanation."
  :type 'sexp
  :group 'calendar)

(defcustom calendar-date-display-form
  (if european-calendar-style
      european-calendar-display-form
    american-calendar-display-form)
  "*Pseudo-pattern governing the way a date appears.

Used by the function `calendar-date-string', a pseudo-pattern is a list of
expressions that can involve the keywords `month', `day', and `year', all
numbers in string form, and `monthname' and `dayname', both alphabetic
strings.  For example, the ISO standard would use the pseudo- pattern

       '(year \"-\" month \"-\" day)

while a typical American form would be

       '(month \"/\" day \"/\" (substring year -2))

and

       '((format \"%9s, %9s %2s, %4s\" dayname monthname day year))

would give the usual American style in fixed-length fields.

See the documentation of the function `calendar-date-string'."
  :type 'sexp
  :group 'calendar)

(defun european-calendar ()
  "Set the interpretation and display of dates to the European style."
  (interactive)
  (setq european-calendar-style t)
  (setq calendar-date-display-form european-calendar-display-form)
  (setq diary-date-forms european-date-diary-pattern)
  (update-calendar-mode-line))

(defun american-calendar ()
  "Set the interpretation and display of dates to the American style."
  (interactive)
  (setq european-calendar-style nil)
  (setq calendar-date-display-form american-calendar-display-form)
  (setq diary-date-forms american-date-diary-pattern)
  (update-calendar-mode-line))

;;;###autoload
(defcustom print-diary-entries-hook 'lpr-buffer
  "*List of functions called after a temporary diary buffer is prepared.
The buffer shows only the diary entries currently visible in the diary
buffer.  The default just does the printing.  Other uses might include, for
example, rearranging the lines into order by day and time, saving the buffer
instead of deleting it, or changing the function used to do the printing."
  :type 'hook
  :group 'diary)

;;;###autoload
(defcustom list-diary-entries-hook nil
  "*List of functions called after diary file is culled for relevant entries.
It is to be used for diary entries that are not found in the diary file.

A function `include-other-diary-files' is provided for use as the value of
this hook.  This function enables you to use shared diary files together
with your own.  The files included are specified in the diary file by lines
of the form

        #include \"filename\"

This is recursive; that is, #include directives in files thus included are
obeyed.  You can change the \"#include\" to some other string by changing
the variable `diary-include-string'.  When you use `include-other-diary-files'
as part of the list-diary-entries-hook, you will probably also want to use the
function `mark-included-diary-files' as part of `mark-diary-entries-hook'.

For example, you could use

     (setq list-diary-entries-hook
       '(include-other-diary-files sort-diary-entries))
     (setq diary-display-hook 'fancy-diary-display)

in your `.emacs' file to cause the fancy diary buffer to be displayed with
diary entries from various included files, each day's entries sorted into
lexicographic order."
  :type 'hook
  :options '(include-other-diary-files sort-diary-entries)
  :group 'diary)

;;;###autoload
(defcustom diary-hook nil
  "*List of functions called after the display of the diary.
Can be used for appointment notification."
  :type 'hook
  :group 'diary)

;;;###autoload
(defcustom diary-display-hook nil
  "*List of functions that handle the display of the diary.
If nil (the default), `simple-diary-display' is used.  Use `ignore' for no
diary display.

Ordinarily, this just displays the diary buffer (with holidays indicated in
the mode line), if there are any relevant entries.  At the time these
functions are called, the variable `diary-entries-list' is a list, in order
by date, of all relevant diary entries in the form of ((MONTH DAY YEAR)
STRING), where string is the diary entry for the given date.  This can be
used, for example, a different buffer for display (perhaps combined with
holidays), or produce hard copy output.

A function `fancy-diary-display' is provided as an alternative
choice for this hook; this function prepares a special noneditable diary
buffer with the relevant diary entries that has neat day-by-day arrangement
with headings.  The fancy diary buffer will show the holidays unless the
variable `holidays-in-diary-buffer' is set to nil.  Ordinarily, the fancy
diary buffer will not show days for which there are no diary entries, even
if that day is a holiday; if you want such days to be shown in the fancy
diary buffer, set the variable `diary-list-include-blanks' to t."
  :type 'hook
  :options '(fancy-diary-display)
  :group 'diary)

;;;###autoload
(defcustom nongregorian-diary-listing-hook nil
  "*List of functions called for listing diary file and included files.
As the files are processed for diary entries, these functions are used
to cull relevant entries.  You can use either or both of
`list-hebrew-diary-entries', `list-islamic-diary-entries' and
`list-bahai-diary-entries'.  The documentation for these functions
describes the style of such diary entries."
  :type 'hook
  :options '(list-hebrew-diary-entries
	     list-islamic-diary-entries
	     list-bahai-diary-entries)
  :group 'diary)

;;;###autoload
(defcustom mark-diary-entries-hook nil
  "*List of functions called after marking diary entries in the calendar.

A function `mark-included-diary-files' is also provided for use as the
`mark-diary-entries-hook'; it enables you to use shared diary files together
with your own.  The files included are specified in the diary file by lines
of the form
        #include \"filename\"
This is recursive; that is, #include directives in files thus included are
obeyed.  You can change the \"#include\" to some other string by changing the
variable `diary-include-string'.  When you use `mark-included-diary-files' as
part of the mark-diary-entries-hook, you will probably also want to use the
function `include-other-diary-files' as part of `list-diary-entries-hook'."
  :type 'hook
  :options '(mark-included-diary-files)
  :group 'diary)

;;;###autoload
(defcustom nongregorian-diary-marking-hook nil
  "*List of functions called for marking diary file and included files.
As the files are processed for diary entries, these functions are used
to cull relevant entries.  You can use either or both of
`mark-hebrew-diary-entries', `mark-islamic-diary-entries' and
`mark-bahai-diary-entries'.  The documentation for these functions
describes the style of such diary entries."
  :type 'hook
  :options '(mark-hebrew-diary-entries
	     mark-islamic-diary-entries
	     mark-bahai-diary-entries)
  :group 'diary)

;;;###autoload
(defcustom diary-list-include-blanks nil
  "*If nil, do not include days with no diary entry in the list of diary entries.
Such days will then not be shown in the fancy diary buffer, even if they
are holidays."
  :type 'boolean
  :group 'diary)

;;;###autoload
(defcustom holidays-in-diary-buffer t
  "*Non-nil means include holidays in the diary display.
The holidays appear in the mode line of the diary buffer, or in the
fancy diary buffer next to the date.  This slows down the diary functions
somewhat; setting it to nil makes the diary display faster."
  :type 'boolean
  :group 'holidays)

(defvar calendar-mark-ring nil)

;;;###autoload
(put 'general-holidays 'risky-local-variable t)
;;;###autoload
(defcustom general-holidays
  '((holiday-fixed 1 1 "New Year's Day")
    (holiday-float 1 1 3 "Martin Luther King Day")
    (holiday-fixed 2 2 "Groundhog Day")
    (holiday-fixed 2 14 "Valentine's Day")
    (holiday-float 2 1 3 "President's Day")
    (holiday-fixed 3 17 "St. Patrick's Day")
    (holiday-fixed 4 1 "April Fools' Day")
    (holiday-float 5 0 2 "Mother's Day")
    (holiday-float 5 1 -1 "Memorial Day")
    (holiday-fixed 6 14 "Flag Day")
    (holiday-float 6 0 3 "Father's Day")
    (holiday-fixed 7 4 "Independence Day")
    (holiday-float 9 1 1 "Labor Day")
    (holiday-float 10 1 2 "Columbus Day")
    (holiday-fixed 10 31 "Halloween")
    (holiday-fixed 11 11 "Veteran's Day")
    (holiday-float 11 4 4 "Thanksgiving"))
  "*General holidays.  Default value is for the United States.
See the documentation for `calendar-holidays' for details."
  :type 'sexp
  :group 'holidays)

;;;###autoload
(put 'oriental-holidays 'risky-local-variable t)
;;;###autoload
(defcustom oriental-holidays
  '((if (fboundp 'atan)
	(holiday-chinese-new-year)))
  "*Oriental holidays.
See the documentation for `calendar-holidays' for details."
  :type 'sexp
  :group 'holidays)

;;;###autoload
(put 'local-holidays 'risky-local-variable t)
;;;###autoload
(defcustom local-holidays nil
  "*Local holidays.
See the documentation for `calendar-holidays' for details."
  :type 'sexp
  :group 'holidays)

;;;###autoload
(put 'other-holidays 'risky-local-variable t)
;;;###autoload
(defcustom other-holidays nil
  "*User defined holidays.
See the documentation for `calendar-holidays' for details."
  :type 'sexp
  :group 'holidays)

;;;###autoload
(put 'hebrew-holidays-1 'risky-local-variable t)
;;;###autoload
(defvar hebrew-holidays-1
  '((holiday-rosh-hashanah-etc)
    (if all-hebrew-calendar-holidays
        (holiday-julian
         11
         (let* ((m displayed-month)
                (y displayed-year)
                (year))
           (increment-calendar-month m y -1)
           (let ((year (extract-calendar-year
                        (calendar-julian-from-absolute
                         (calendar-absolute-from-gregorian
                          (list m 1 y))))))
             (if (zerop (% (1+ year) 4))
                 22
               21))) "\"Tal Umatar\" (evening)"))))

;;;###autoload
(put 'hebrew-holidays-2 'risky-local-variable t)
;;;###autoload
(defvar hebrew-holidays-2
  '((if all-hebrew-calendar-holidays
        (holiday-hanukkah)
      (holiday-hebrew 9 25 "Hanukkah"))
    (if all-hebrew-calendar-holidays
      (holiday-hebrew
       10
       (let ((h-year (extract-calendar-year
                      (calendar-hebrew-from-absolute
                       (calendar-absolute-from-gregorian
                        (list displayed-month 28 displayed-year))))))
         (if (= (% (calendar-absolute-from-hebrew (list 10 10 h-year))
                   7)
                6)
             11 10))
       "Tzom Teveth"))
    (if all-hebrew-calendar-holidays
        (holiday-hebrew 11 15 "Tu B'Shevat"))))

;;;###autoload
(put 'hebrew-holidays-3 'risky-local-variable t)
;;;###autoload
(defvar hebrew-holidays-3
  '((if all-hebrew-calendar-holidays
        (holiday-hebrew
         11
         (let ((m displayed-month)
               (y displayed-year))
           (increment-calendar-month m y 1)
           (let* ((h-year (extract-calendar-year
                           (calendar-hebrew-from-absolute
                            (calendar-absolute-from-gregorian
                             (list m
                                   (calendar-last-day-of-month m y)
                                   y)))))
                  (s-s
                   (calendar-hebrew-from-absolute
                    (if (=
                         (% (calendar-absolute-from-hebrew
                             (list 7 1 h-year))
                            7)
                         6)
                        (calendar-dayname-on-or-before
                         6 (calendar-absolute-from-hebrew
                            (list 11 17 h-year)))
                      (calendar-dayname-on-or-before
                       6 (calendar-absolute-from-hebrew
                          (list 11 16 h-year))))))
                  (day (extract-calendar-day s-s)))
             day))
         "Shabbat Shirah"))))

;;;###autoload
(put 'hebrew-holidays-4 'risky-local-variable t)
;;;###autoload
(defvar hebrew-holidays-4
  '((holiday-passover-etc)
    (if (and all-hebrew-calendar-holidays
             (let* ((m displayed-month)
                    (y displayed-year)
                    (year))
               (increment-calendar-month m y -1)
               (let ((year (extract-calendar-year
                            (calendar-julian-from-absolute
                             (calendar-absolute-from-gregorian
                              (list m 1 y))))))
                 (= 21 (% year 28)))))
        (holiday-julian 3 26 "Kiddush HaHamah"))
    (if all-hebrew-calendar-holidays
        (holiday-tisha-b-av-etc))))

;;;###autoload
(put 'hebrew-holidays 'risky-local-variable t)
;;;###autoload
(defcustom hebrew-holidays (append hebrew-holidays-1 hebrew-holidays-2
				hebrew-holidays-3 hebrew-holidays-4)
  "*Jewish holidays.
See the documentation for `calendar-holidays' for details."
  :type 'sexp
  :group 'holidays)

;;;###autoload
(put 'christian-holidays 'risky-local-variable t)
;;;###autoload
(defcustom christian-holidays
  '((if all-christian-calendar-holidays
        (holiday-fixed 1 6 "Epiphany"))
    (holiday-easter-etc)
    (if all-christian-calendar-holidays
        (holiday-greek-orthodox-easter))
    (if all-christian-calendar-holidays
        (holiday-fixed 8 15 "Assumption"))
    (if all-christian-calendar-holidays
        (holiday-advent))
    (holiday-fixed 12 25 "Christmas")
    (if all-christian-calendar-holidays
        (holiday-julian 12 25 "Eastern Orthodox Christmas")))
  "*Christian holidays.
See the documentation for `calendar-holidays' for details."
  :type 'sexp
  :group 'holidays)

;;;###autoload
(put 'islamic-holidays 'risky-local-variable t)
;;;###autoload
(defcustom islamic-holidays
  '((holiday-islamic
     1 1
     (format "Islamic New Year %d"
             (let ((m displayed-month)
                   (y displayed-year))
               (increment-calendar-month m y 1)
               (extract-calendar-year
                (calendar-islamic-from-absolute
                 (calendar-absolute-from-gregorian
                  (list
                   m (calendar-last-day-of-month m y) y)))))))
    (if all-islamic-calendar-holidays
        (holiday-islamic 1 10 "Ashura"))
    (if all-islamic-calendar-holidays
        (holiday-islamic 3 12 "Mulad-al-Nabi"))
    (if all-islamic-calendar-holidays
        (holiday-islamic 7 26 "Shab-e-Mi'raj"))
    (if all-islamic-calendar-holidays
        (holiday-islamic 8 15 "Shab-e-Bara't"))
    (holiday-islamic 9 1 "Ramadan Begins")
    (if all-islamic-calendar-holidays
        (holiday-islamic 9 27 "Shab-e Qadr"))
    (if all-islamic-calendar-holidays
        (holiday-islamic 10 1 "Id-al-Fitr"))
    (if all-islamic-calendar-holidays
        (holiday-islamic 12 10 "Id-al-Adha")))
  "*Islamic holidays.
See the documentation for `calendar-holidays' for details."
  :type 'sexp
  :group 'holidays)

;;;###autoload
(put 'bahai-holidays 'risky-local-variable t)
;;;###autoload
(defcustom bahai-holidays
  '((holiday-fixed
     3 21
     (format "Baha'i New Year (Naw-Ruz) %d" (- displayed-year (1- 1844))))
    (holiday-fixed  4 21 "First Day of Ridvan")
    (if all-bahai-calendar-holidays
	(holiday-fixed  4 22 "Second Day of Ridvan"))
    (if all-bahai-calendar-holidays
	(holiday-fixed  4 23 "Third Day of Ridvan"))
    (if all-bahai-calendar-holidays
	(holiday-fixed  4 24 "Fourth Day of Ridvan"))
    (if all-bahai-calendar-holidays
	(holiday-fixed  4 25 "Fifth Day of Ridvan"))
    (if all-bahai-calendar-holidays
	(holiday-fixed  4 26 "Sixth Day of Ridvan"))
    (if all-bahai-calendar-holidays
	(holiday-fixed  4 27 "Seventh Day of Ridvan"))
    (if all-bahai-calendar-holidays
	(holiday-fixed  4 28 "Eighth Day of Ridvan"))
    (holiday-fixed  4 29 "Ninth Day of Ridvan")
    (if all-bahai-calendar-holidays
	(holiday-fixed  4 30 "Tenth Day of Ridvan"))
    (if all-bahai-calendar-holidays
	(holiday-fixed  5  1 "Eleventh Day of Ridvan"))
    (holiday-fixed  5  2 "Twelfth Day of Ridvan")
    (holiday-fixed  5 23 "Declaration of the Bab")
    (holiday-fixed  5 29 "Ascension of Baha'u'llah")
    (holiday-fixed  7  9 "Martyrdom of the Bab")
    (holiday-fixed 10 20 "Birth of the Bab")
    (holiday-fixed 11 12 "Birth of Baha'u'llah")
    (if all-bahai-calendar-holidays
	(holiday-fixed 11 26 "Day of the Covenant"))
    (if all-bahai-calendar-holidays
	(holiday-fixed 11 28 "Ascension of `Abdu'l-Baha")))
  "*Baha'i holidays.
See the documentation for `calendar-holidays' for details."
  :type 'sexp
  :group 'holidays)

;;;###autoload
(put 'solar-holidays 'risky-local-variable t)
;;;###autoload
(defcustom solar-holidays
  '((if (fboundp 'atan)
	(solar-equinoxes-solstices))
    (if (progn
	  (require 'cal-dst)
	  t)
      (funcall
       'holiday-sexp
        calendar-daylight-savings-starts
        '(format "Daylight Savings Time Begins %s"
                  (if (fboundp 'atan)
                      (solar-time-string
                       (/ calendar-daylight-savings-starts-time (float 60))
                       calendar-standard-time-zone-name)
                    ""))))
    (funcall
     'holiday-sexp
     calendar-daylight-savings-ends
     '(format "Daylight Savings Time Ends %s"
              (if (fboundp 'atan)
                  (solar-time-string
                   (/ calendar-daylight-savings-ends-time (float 60))
                   calendar-daylight-time-zone-name)
                ""))))
  "*Sun-related holidays.
See the documentation for `calendar-holidays' for details."
  :type 'sexp
  :group 'holidays)

;;;###autoload
(put 'calendar-holidays 'risky-local-variable t)
(defcustom calendar-holidays
  (append general-holidays local-holidays other-holidays
          christian-holidays hebrew-holidays islamic-holidays
          bahai-holidays oriental-holidays solar-holidays)
  "*List of notable days for the command \\[holidays].

Additional holidays are easy to add to the list, just put them in the
list `other-holidays' in your .emacs file.  Similarly, by setting any
of `general-holidays', `local-holidays' `christian-holidays',
`hebrew-holidays', `islamic-holidays', `bahai-holidays',
`oriental-holidays', or `solar-holidays' to nil in your .emacs file,
you can eliminate unwanted categories of holidays.  The intention is
that (in the US) `local-holidays' be set in site-init.el and
`other-holidays' be set by the user.

Entries on the list are expressions that return (possibly empty) lists of
items of the form ((month day year) string) of a holiday in the in the
three-month period centered around `displayed-month' of `displayed-year'.
Several basic functions are provided for this purpose:

    (holiday-fixed MONTH DAY STRING) is a fixed date on the Gregorian calendar
    (holiday-float MONTH DAYNAME K STRING &optional day) is the Kth DAYNAME in
                               MONTH on the Gregorian calendar (0 for Sunday,
                               etc.); K<0 means count back from the end of the
                               month.  An optional parameter DAY means the Kth
                               DAYNAME after/before MONTH DAY.
    (holiday-hebrew MONTH DAY STRING)  a fixed date on the Hebrew calendar
    (holiday-islamic MONTH DAY STRING) a fixed date on the Islamic calendar
    (holiday-bahai MONTH DAY STRING)   a fixed date on the Baha'i calendar
    (holiday-julian MONTH DAY STRING)  a fixed date on the Julian calendar
    (holiday-sexp SEXP STRING) SEXP is a Gregorian-date-valued expression
                               in the variable `year'; if it evaluates to
                               a visible date, that's the holiday; if it
                               evaluates to nil, there's no holiday.  STRING
                               is an expression in the variable `date'.

For example, to add Bastille Day, celebrated in France on July 14, add

     (holiday-fixed 7 14 \"Bastille Day\")

to the list.  To add Hurricane Supplication Day, celebrated in the Virgin
Islands on the fourth Monday in August, add

     (holiday-float 8 1 4 \"Hurricane Supplication Day\")

to the list (the last Monday would be specified with `-1' instead of `4').
To add the last day of Hanukkah to the list, use

     (holiday-hebrew 10 2 \"Last day of Hanukkah\")

since the Hebrew months are numbered with 1 starting from Nisan, while to
add the Islamic feast celebrating Mohammed's birthday use

     (holiday-islamic 3 12 \"Mohammed's Birthday\")

since the Islamic months are numbered from 1 starting with Muharram.  To
add an entry for the Baha'i festival of Ridvan, use

     (holiday-bahai 2 13 \"Festival of Ridvan\")

since the Baha'i months are numbered from 1 starting with Baha.  To
add Thomas Jefferson's birthday, April 2, 1743 (Julian), use

     (holiday-julian 4 2 \"Jefferson's Birthday\")

To include a holiday conditionally, use the sexp form or a conditional.  For
example, to include American presidential elections, which occur on the first
Tuesday after the first Monday in November of years divisible by 4, add

     (holiday-sexp
       '(if (zerop (% year 4))
           (calendar-gregorian-from-absolute
             (1+ (calendar-dayname-on-or-before
                   1 (+ 6 (calendar-absolute-from-gregorian
                            (list 11 1 year)))))))
       \"US Presidential Election\")

or

     (if (zerop (% displayed-year 4))
         (holiday-fixed 11
                (extract-calendar-day
                 (calendar-gregorian-from-absolute
                  (1+ (calendar-dayname-on-or-before
                       1 (+ 6 (calendar-absolute-from-gregorian
                               (list 11 1 displayed-year)))))))
                \"US Presidential Election\"))

to the list.  To include the phases of the moon, add

     (lunar-phases)

to the holiday list, where `lunar-phases' is an Emacs-Lisp function that
you've written to return a (possibly empty) list of the relevant VISIBLE dates
with descriptive strings such as

     (((2 6 1989) \"New Moon\") ((2 12 1989) \"First Quarter Moon\") ... )."
  :type 'sexp
  :group 'holidays)

(defconst calendar-buffer "*Calendar*"
  "Name of the buffer used for the calendar.")

(defconst holiday-buffer "*Holidays*"
  "Name of the buffer used for the displaying the holidays.")

(defconst fancy-diary-buffer "*Fancy Diary Entries*"
  "Name of the buffer used for the optional fancy display of the diary.")

(defconst other-calendars-buffer "*Other Calendars*"
  "Name of the buffer used for the display of date on other calendars.")

(defconst lunar-phases-buffer "*Phases of Moon*"
  "Name of the buffer used for the lunar phases.")

(defmacro increment-calendar-month (mon yr n)
  "Increment the variables MON and YR by N months.
Forward if N is positive or backward if N is negative.
A negative YR is interpreted as BC; -1 being 1 BC, and so on."
  `(let (macro-y)
     (if (< ,yr 0) (setq ,yr (1+ ,yr))) ; -1 BC -> 0 AD, etc
     (setq macro-y (+ (* ,yr 12) ,mon -1 ,n)
           ,mon (1+ (mod macro-y 12))
           ,yr (/ macro-y 12))
     (and (< macro-y 0) (> ,mon 1) (setq ,yr (1- ,yr)))
     (if (< ,yr 1) (setq ,yr (1- ,yr))))) ; 0 AD -> -1 BC, etc

(defmacro calendar-for-loop (var from init to final do &rest body)
  "Execute a for loop."
  `(let ((,var (1- ,init)))
    (while (>= ,final (setq ,var (1+ ,var)))
      ,@body)))

(defmacro calendar-sum (index initial condition expression)
  "For INDEX = INITIAL et seq, as long as CONDITION holds, sum EXPRESSION."
  `(let ((,index ,initial)
         (sum 0))
    (while ,condition
      (setq sum (+ sum ,expression))
      (setq ,index (1+ ,index)))
    sum))

;; The following are in-line for speed; they can be called thousands of times
;; when looking up holidays or processing the diary.  Here, for example, are
;; the numbers of calls to calendar/diary/holiday functions in preparing the
;; fancy diary display, for a moderately complex diary file, with functions
;; used instead of macros.  There were a total of 10000 such calls:
;;
;;  1934   extract-calendar-month
;;  1852   extract-calendar-year
;;  1819   extract-calendar-day
;;   845   calendar-leap-year-p
;;   837   calendar-day-number
;;   775   calendar-absolute-from-gregorian
;;   346   calendar-last-day-of-month
;;   286   hebrew-calendar-last-day-of-month
;;   188   hebrew-calendar-leap-year-p
;;   180   hebrew-calendar-elapsed-days
;;   163   hebrew-calendar-last-month-of-year
;;    66   calendar-date-compare
;;    65   hebrew-calendar-days-in-year
;;    60   calendar-absolute-from-julian
;;    50   calendar-absolute-from-hebrew
;;    43   calendar-date-equal
;;    38   calendar-gregorian-from-absolute
;;     .
;;     .
;;     .
;;
;; The use of these seven macros eliminates the overhead of 92% of the function
;; calls; it's faster this way.

(defsubst extract-calendar-month (date)
  "Extract the month part of DATE which has the form (month day year)."
  (car date))

(defsubst extract-calendar-day (date)
  "Extract the day part of DATE which has the form (month day year)."
  (car (cdr date)))

(defsubst extract-calendar-year (date)
  "Extract the year part of DATE which has the form (month day year)."
  (car (cdr (cdr date))))

(defsubst calendar-leap-year-p (year)
  "Return t if YEAR is a Gregorian leap year.
A negative year is interpreted as BC; -1 being 1 BC, and so on."
  ;; 1 BC = 0 AD, 2 BC acts like 1 AD, etc.
  (if (< year 0) (setq year (1- (abs year))))
  (and (zerop (% year 4))
       (or (not (zerop (% year 100)))
           (zerop (% year 400)))))

;; The foregoing is a bit faster, but not as clear as the following:
;;
;;(defsubst calendar-leap-year-p (year)
;;  "Returns t if YEAR is a Gregorian leap year."
;;  (or
;;    (and (=  (% year   4) 0)
;;         (/= (% year 100) 0))
;;    (= (% year 400) 0)))

(defsubst calendar-last-day-of-month (month year)
  "The last day in MONTH during YEAR."
  (if (and (= month 2) (calendar-leap-year-p year))
      29
    (aref [31 28 31 30 31 30 31 31 30 31 30 31] (1- month))))

;; An explanation of the calculation can be found in PascAlgorithms by
;; Edward and Ruth Reingold, Scott-Foresman/Little, Brown, 1988.

(defsubst calendar-day-number (date)
  "Return the day number within the year of the date DATE.
For example, (calendar-day-number '(1 1 1987)) returns the value 1,
while (calendar-day-number '(12 31 1980)) returns 366."
    (let* ((month (extract-calendar-month date))
           (day (extract-calendar-day date))
           (year (extract-calendar-year date))
         (day-of-year (+ day (* 31 (1- month)))))
      (if (> month 2)
          (progn
            (setq day-of-year (- day-of-year (/ (+ 23 (* 4 month)) 10)))
            (if (calendar-leap-year-p year)
                (setq day-of-year (1+ day-of-year)))))
      day-of-year))

(defsubst calendar-absolute-from-gregorian (date)
  "The number of days elapsed between the Gregorian date 12/31/1 BC and DATE.
The Gregorian date Sunday, December 31, 1 BC is imaginary.
DATE is a list of the form (month day year).  A negative year is
interpreted as BC; -1 being 1 BC, and so on.  Dates before 12/31/1 BC
return negative results."
  (let ((year (extract-calendar-year date))
        offset-years)
    (cond ((= year 0)
           (error "There was no year zero"))
          ((> year 0)
           (setq offset-years (1- year))
           (+ (calendar-day-number date) ; Days this year
              (* 365 offset-years)       ; + Days in prior years
              (/ offset-years 4)         ; + Julian leap years
              (- (/ offset-years 100))   ; - century years
              (/ offset-years 400)))     ; + Gregorian leap years
          (t
           ;; Years between date and 1 BC, excluding 1 BC (1 for 2 BC, etc).
           (setq offset-years (abs (1+ year)))
           (- (calendar-day-number date)
              (* 365 offset-years)
              (/ offset-years 4)
              (- (/ offset-years 100))
              (/ offset-years 400)
              (calendar-day-number '(12 31 -1))))))) ; days in year 1 BC

(autoload 'calendar-goto-today "cal-move"
  "Reposition the calendar window so the current date is visible."
  t)

(autoload 'calendar-forward-month "cal-move"
  "Move the cursor forward ARG months."
  t)

(autoload 'calendar-forward-year "cal-move"
  "Move the cursor forward by ARG years."
  t)

(autoload 'calendar-backward-month "cal-move"
  "Move the cursor backward by ARG months."
  t)

(autoload 'calendar-backward-year "cal-move"
  "Move the cursor backward ARG years."
  t)

(autoload 'scroll-calendar-left "cal-move"
  "Scroll the displayed calendar left by ARG months."
  t)

(autoload 'scroll-calendar-right "cal-move"
  "Scroll the displayed calendar window right by ARG months."
  t)

(autoload 'scroll-calendar-left-three-months "cal-move"
  "Scroll the displayed calendar window left by 3*ARG months."
  t)

(autoload 'scroll-calendar-right-three-months "cal-move"
  "Scroll the displayed calendar window right by 3*ARG months."
  t)

(autoload 'calendar-cursor-to-nearest-date "cal-move"
  "Move the cursor to the closest date."
  t)

(autoload 'calendar-forward-day "cal-move"
  "Move the cursor forward ARG days."
  t)

(autoload 'calendar-backward-day "cal-move"
  "Move the cursor back ARG days."
  t)

(autoload 'calendar-forward-week "cal-move"
  "Move the cursor forward ARG weeks."
  t)

(autoload 'calendar-backward-week "cal-move"
  "Move the cursor back ARG weeks."
  t)

(autoload 'calendar-beginning-of-week "cal-move"
  "Move the cursor back ARG calendar-week-start-day's."
  t)

(autoload 'calendar-end-of-week "cal-move"
  "Move the cursor forward ARG calendar-week-start-day+6's."
  t)

(autoload 'calendar-beginning-of-month "cal-move"
  "Move the cursor backward ARG month beginnings."
  t)

(autoload 'calendar-end-of-month "cal-move"
  "Move the cursor forward ARG month ends."
  t)

(autoload 'calendar-beginning-of-year "cal-move"
  "Move the cursor backward ARG year beginnings."
  t)

(autoload 'calendar-end-of-year "cal-move"
  "Move the cursor forward ARG year beginnings."
  t)

(autoload 'calendar-cursor-to-visible-date "cal-move"
  "Move the cursor to DATE that is on the screen."
  t)

(autoload 'calendar-goto-date "cal-move"
  "Move cursor to DATE."
  t)

(autoload 'calendar-goto-day-of-year "cal-move"
  "Move cursor to day of year."
  t)

(autoload 'calendar-only-one-frame-setup "cal-x"
 "Start calendar and display it in a dedicated frame.")

(autoload 'calendar-one-frame-setup "cal-x"
  "Start calendar and display it in a dedicated frame together with the diary.")

(autoload 'calendar-two-frame-setup "cal-x"
  "Start calendar and diary in separate, dedicated frames.")

;;;###autoload
(defcustom calendar-setup nil
  "The frame setup of the calendar.
The choices are: `one-frame' (calendar and diary together in one separate,
dedicated frame); `two-frames' (calendar and diary in separate, dedicated
frames); `calendar-only' (calendar in a separate, dedicated frame); with
any other value the current frame is used.  Using any of the first 
three options overrides the value of `view-diary-entries-initially'."
  :type '(choice
          (const :tag "calendar and diary in separate frame" one-frame)
          (const :tag "calendar and diary each in own frame" two-frames)
          (const :tag "calendar in separate frame" calendar-only)
          (const :tag "use current frame" nil))
  :group 'calendar)

;;;###autoload
(defun calendar (&optional arg)
  "Choose between the one frame, two frame, or basic calendar displays.
If called with an optional prefix argument, prompts for month and year.

The original function `calendar' has been renamed `calendar-basic-setup'.
See the documentation of that function for more information."
  (interactive "P")
  (cond ((equal calendar-setup 'one-frame) (calendar-one-frame-setup arg))
        ((equal calendar-setup 'two-frames) (calendar-two-frame-setup arg))
        ((equal calendar-setup 'calendar-only)
         (calendar-only-one-frame-setup arg))
        (t (calendar-basic-setup arg))))

(defun calendar-basic-setup (&optional arg)
  "Display a three-month calendar in another window.
The three months appear side by side, with the current month in the middle
surrounded by the previous and next months.  The cursor is put on today's date.

If called with an optional prefix argument, prompts for month and year.

This function is suitable for execution in a .emacs file; appropriate setting
of the variable `view-diary-entries-initially' will cause the diary entries for
the current date to be displayed in another window.  The value of the variable
`number-of-diary-entries' controls the number of days of diary entries
displayed upon initial display of the calendar.

Once in the calendar window, future or past months can be moved into view.
Arbitrary months can be displayed, or the calendar can be scrolled forward
or backward.

The cursor can be moved forward or backward by one day, one week, one month,
or one year.  All of these commands take prefix arguments which, when negative,
cause movement in the opposite direction.  For convenience, the digit keys
and the minus sign are automatically prefixes.  The window is replotted as
necessary to display the desired date.

Diary entries can be marked on the calendar or displayed in another window.

Use \\[describe-mode] for details of the key bindings in the calendar window.

The Gregorian calendar is assumed.

After loading the calendar, the hooks given by the variable
`calendar-load-hook' are run.  This is the place to add key bindings to the
calendar-mode-map.

After preparing the calendar window initially, the hooks given by the variable
`initial-calendar-window-hook' are run.

The hooks given by the variable `today-visible-calendar-hook' are run
every time the calendar window gets scrolled, if the current date is visible
in the window.  If it is not visible, the hooks given by the variable
`today-invisible-calendar-hook' are run.  Thus, for example, setting
`today-visible-calendar-hook' to 'calendar-star-date will cause today's date
to be replaced by asterisks to highlight it whenever it is in the window."
  (interactive "P")
  (set-buffer (get-buffer-create calendar-buffer))
  (calendar-mode)
  (let* ((pop-up-windows t)
         (split-height-threshold 1000)
         (date (if arg
                   (calendar-read-date t)
                 (calendar-current-date)))
         (month (extract-calendar-month date))
         (year (extract-calendar-year date)))
    (pop-to-buffer calendar-buffer)
    (increment-calendar-month month year (- calendar-offset))
    (generate-calendar-window month year)
    (if (and view-diary-entries-initially (calendar-date-is-visible-p date))
        (view-diary-entries
         (if (vectorp number-of-diary-entries)
             (aref number-of-diary-entries (calendar-day-of-week date))
           number-of-diary-entries))))
  (let* ((diary-buffer (get-file-buffer diary-file))
         (diary-window (if diary-buffer (get-buffer-window diary-buffer)))
         (split-height-threshold (if diary-window 2 1000)))
    (if view-calendar-holidays-initially
        (list-calendar-holidays)))
  (run-hooks 'initial-calendar-window-hook))

(autoload 'view-diary-entries "diary-lib"
  "Prepare and display a buffer with diary entries.
Searches your diary file for entries that match ARG days starting with
the date indicated by the cursor position in the displayed three-month
calendar."
  t)

(autoload 'calendar-sunrise-sunset "solar"
  "Local time of sunrise and sunset for date under cursor."
  t)

(autoload 'calendar-phases-of-moon "lunar"
  "Create a buffer of the phases of the moon for the current calendar window."
  t)

(autoload 'calendar-print-french-date "cal-french"
  "Show the French Revolutionary calendar equivalent of the date under the cursor."
  t)

(autoload 'calendar-goto-french-date "cal-french"
 "Move cursor to French Revolutionary date."
  t)

(autoload 'calendar-french-date-string "cal-french"
  "String of French Revolutionary date of Gregorian date."
  t)

(autoload 'calendar-mayan-date-string "cal-mayan"
  "String of Mayan date of Gregorian date."
  t)

(autoload 'calendar-print-mayan-date "cal-mayan"
  "Show the Mayan long count, Tzolkin, and Haab equivalents of the date under the cursor."
  t)

(autoload 'calendar-goto-mayan-long-count-date "cal-mayan"
 "Move cursor to Mayan long count date."
  t)

(autoload 'calendar-next-haab-date "cal-mayan"
  "Move cursor to next instance of Mayan Haab date."
  t)

(autoload 'calendar-previous-haab-date "cal-mayan"
  "Move cursor to previous instance of Mayan Haab date."
  t)

(autoload 'calendar-next-tzolkin-date "cal-mayan"
  "Move cursor to next instance of Mayan Tzolkin date."
  t)

(autoload 'calendar-previous-tzolkin-date "cal-mayan"
  "Move cursor to previous instance of Mayan Tzolkin date."
  t)

(autoload 'calendar-next-calendar-round-date "cal-mayan"
  "Move cursor to next instance of Mayan Haab/Tzolkin combination."
  t)

(autoload 'calendar-previous-calendar-round-date "cal-mayan"
  "Move cursor to previous instance of Mayan Haab/Tzolkin combination."
  t)

(autoload 'calendar-goto-chinese-date "cal-china"
   "Move cursor to Chinese date."
   t)

(autoload 'calendar-print-chinese-date "cal-china"
 "Show the Chinese date equivalents of date."
 t)

(autoload 'calendar-chinese-date-string "cal-china"
  "String of Chinese date of Gregorian date."
  t)

(autoload 'calendar-absolute-from-astro  "cal-julian"
  "Absolute date of astronomical (Julian) day number D."
  t )

(autoload 'calendar-astro-from-absolute "cal-julian"
  "Astronomical (Julian) day number of absolute date D.")

(autoload 'calendar-astro-date-string "cal-julian"
  "String of astronomical (Julian) day number of Gregorian date."
  t)

(autoload 'calendar-goto-astro-day-number "cal-julian"
   "Move cursor to astronomical (Julian) day number."
   t)

(autoload 'calendar-print-astro-day-number "cal-julian"
   "Show the astro date equivalents of date."
   t)

(autoload 'calendar-julian-from-absolute "cal-julian"
  "Compute the Julian (month day year) corresponding to the absolute DATE.
The absolute date is the number of days elapsed since the (imaginary)
Gregorian date Sunday, December 31, 1 BC.")

(autoload 'calendar-goto-julian-date "cal-julian"
  "Move cursor to Julian DATE; echo Julian date unless NOECHO is t."
  t)

(autoload 'calendar-print-julian-date "cal-julian"
  "Show the Julian calendar equivalent of the date under the cursor."
  t)

(autoload 'calendar-julian-date-string "cal-julian"
  "String of Julian date of Gregorian DATE.
Defaults to today's date if DATE is not given.
Driven by the variable `calendar-date-display-form'.")

(autoload 'calendar-goto-iso-date "cal-iso"
  "Move cursor to ISO date."
  t)

(autoload 'calendar-print-iso-date "cal-iso"
  "Show the ISO date equivalents of date."
  t)

(autoload 'calendar-iso-date-string "cal-iso"
  "String of ISO date of Gregorian date."
  t)

(autoload 'calendar-goto-islamic-date "cal-islam"
  "Move cursor to Islamic date."
  t)

(autoload 'calendar-print-islamic-date "cal-islam"
  "Show the Islamic date equivalents of date."
  t)

(autoload 'calendar-islamic-date-string "cal-islam"
  "String of Islamic date of Gregorian date."
  t)

(autoload 'calendar-print-bahai-date "cal-bahai"
  "Show the Baha'i date equivalents of date."
  t)

(autoload 'calendar-bahai-date-string "cal-bahai"
  "String of Baha'i date of Gregorian date."
  t)

(autoload 'calendar-goto-hebrew-date "cal-hebrew"
  "Move cursor to Hebrew date date."
  t)

(autoload 'calendar-print-hebrew-date "cal-hebrew"
  "Show the Hebrew date equivalents of date."
  t)

(autoload 'calendar-hebrew-date-string "cal-hebrew"
  "String of Hebrew date of Gregorian date."
  t)

(autoload 'calendar-goto-coptic-date "cal-coptic"
   "Move cursor to Coptic date date."
   t)

(autoload 'calendar-print-coptic-date "cal-coptic"
 "Show the Coptic date equivalents of date."
 t)

(autoload 'calendar-coptic-date-string "cal-coptic"
  "String of Coptic date of Gregorian date."
  t)

(autoload 'calendar-goto-ethiopic-date "cal-coptic"
   "Move cursor to Ethiopic date date."
   t)

(autoload 'calendar-print-ethiopic-date "cal-coptic"
 "Show the Ethiopic date equivalents of date."
 t)

(autoload 'calendar-ethiopic-date-string "cal-coptic"
  "String of Ethiopic date of Gregorian date."
  t)

(autoload 'calendar-goto-persian-date "cal-persia"
   "Move cursor to Persian date date."
   t)

(autoload 'calendar-print-persian-date "cal-persia"
 "Show the Persian date equivalents of date."
 t)

(autoload 'calendar-persian-date-string "cal-persia"
  "String of Persian date of Gregorian date."
  t)

(autoload 'show-all-diary-entries "diary-lib"
  "Show all of the diary entries in the diary file.
This function gets rid of the selective display of the diary file so that
all entries, not just some, are visible.  If there is no diary buffer, one
is created."
  t)

(autoload 'mark-diary-entries "diary-lib"
  "Mark days in the calendar window that have diary entries.
Each entry in diary file visible in the calendar window is marked."
  t)

(autoload 'make-diary-entry "diary-lib"
  "Insert a diary entry STRING which may be NONMARKING in FILE."
  t)

(autoload 'insert-diary-entry "diary-lib"
  "Insert a diary entry for the date indicated by point."
  t)

(autoload 'insert-weekly-diary-entry "diary-lib"
  "Insert a weekly diary entry for the day of the week indicated by point."
  t)


(autoload 'insert-monthly-diary-entry "diary-lib"
  "Insert a monthly diary entry for the day of the month indicated by point."
  t)

(autoload 'insert-yearly-diary-entry "diary-lib"
  "Insert an annual diary entry for the day of the year indicated by point."
  t)

(autoload 'insert-anniversary-diary-entry "diary-lib"
  "Insert an anniversary diary entry for the date indicated by point."
  t)

(autoload 'insert-block-diary-entry "diary-lib"
  "Insert a block diary entry for the dates indicated by point and mark."
  t)

(autoload 'insert-cyclic-diary-entry "diary-lib"
  "Insert a cyclic diary entry starting at the date indicated by point."
  t)

(autoload 'insert-hebrew-diary-entry "cal-hebrew"
  "Insert a diary entry for the Hebrew date corresponding to the date
indicated by point."
  t)

(autoload 'insert-monthly-hebrew-diary-entry "cal-hebrew"
  "Insert a monthly diary entry for the day of the Hebrew month corresponding
to the date indicated by point."
  t)

(autoload 'insert-yearly-hebrew-diary-entry "cal-hebrew"
  "Insert an annual diary entry for the day of the Hebrew year corresponding
to the date indicated by point."
  t)

(autoload 'insert-islamic-diary-entry "cal-islam"
  "Insert a diary entry for the Islamic date corresponding to the date
indicated by point."
  t)

(autoload 'insert-monthly-islamic-diary-entry "cal-islam"
  "Insert a monthly diary entry for the day of the Islamic month corresponding
to the date indicated by point."
  t)

(autoload 'insert-yearly-islamic-diary-entry "cal-islam"
  "Insert an annual diary entry for the day of the Islamic year corresponding
to the date indicated by point."
  t)

(autoload 'insert-bahai-diary-entry "cal-bahai"
  "Insert a diary entry for the Baha'i date corresponding to the date
indicated by point."
  t)

(autoload 'insert-monthly-bahai-diary-entry "cal-bahai"
  "Insert a monthly diary entry for the day of the Baha'i month corresponding
to the date indicated by point."
  t)

(autoload 'insert-yearly-bahai-diary-entry "cal-bahai"
  "Insert an annual diary entry for the day of the Baha'i year corresponding
to the date indicated by point."
  t)

(autoload 'list-calendar-holidays "holidays"
  "Create a buffer containing the holidays for the current calendar window.
The holidays are those in the list `calendar-notable-days'.  Returns t if any
holidays are found, nil if not."
  t)

(autoload 'cal-tex-cursor-month "cal-tex"
  "Make a buffer with LaTeX commands for the month cursor is on.
Optional prefix argument specifies number of months to be produced.
Calendar is condensed onto one page.")

(autoload 'cal-tex-cursor-month-landscape "cal-tex"
  "Make a buffer with LaTeX commands for the month cursor is on.
Optional prefix argument specifies number of months to be produced.")

(autoload 'cal-tex-cursor-day "cal-tex"
  "Make a buffer with LaTeX commands for the day cursor is on.")

(autoload 'cal-tex-cursor-week "cal-tex"
  "Make a buffer with LaTeX commands for a two-page one-week calendar.
It applies to the week that point is in.
Optional prefix argument specifies number of weeks.
Holidays are included if `cal-tex-holidays' is t.")

(autoload 'cal-tex-cursor-week2 "cal-tex"
  "Make a buffer with LaTeX commands for a two-page one-week calendar.
It applies to the week that point is in.
Optional prefix argument specifies number of weeks.
Holidays are included if `cal-tex-holidays' is t.")

(autoload 'cal-tex-cursor-week-iso "cal-tex"
  "Make a buffer with LaTeX commands for a one page ISO-style weekly calendar.
Optional prefix argument specifies number of weeks.
Diary entries are included if `cal-tex-diary' is t.
Holidays are included if `cal-tex-holidays' is t.")

(autoload 'cal-tex-cursor-week-monday "cal-tex"
  "Make a buffer with LaTeX commands for a two-page one-week calendar.
It applies to the week that point is in, and starts on Monday.
Optional prefix argument specifies number of weeks.
Holidays are included if `cal-tex-holidays' is t.")

(autoload 'cal-tex-cursor-filofax-2week "cal-tex"
  "Two-weeks-at-a-glance Filofax style calendar for week indicated by cursor.
Optional prefix argument specifies number of weeks.
Diary entries are included if cal-tex-diary is t.
Holidays are included if `cal-tex-holidays' is t.")

(autoload 'cal-tex-cursor-filofax-week "cal-tex"
  "One-week-at-a-glance Filofax style calendar for week indicated by cursor.
Optional prefix argument specifies number of weeks.
Weeks start on Monday.
Diary entries are included if cal-tex-diary is t.
Holidays are included if `cal-tex-holidays' is t.")

(autoload 'cal-tex-cursor-filofax-daily "cal-tex"
  "Day-per-page Filofax style calendar for week indicated by cursor.
Optional prefix argument specifies number of weeks.  Weeks start on Monday.
Diary entries are included if `cal-tex-diary' is t.
Holidays are included if `cal-tex-holidays' is t.")

(autoload 'cal-tex-cursor-year "cal-tex"
  "Make a buffer with LaTeX commands for a year's calendar.
Optional prefix argument specifies number of years.")

(autoload 'cal-tex-cursor-year-landscape "cal-tex"
  "Make a buffer with LaTeX commands for a year's calendar (landscape).
Optional prefix argument specifies number of years.")

(autoload 'cal-tex-cursor-filofax-year "cal-tex"
  "Make a buffer with LaTeX commands for a year's calendar (Filofax).
Optional prefix argument specifies number of years.")

(autoload 'mark-calendar-holidays "holidays"
  "Mark notable days in the calendar window."
  t)

(autoload 'calendar-cursor-holidays "holidays"
  "Find holidays for the date specified by the cursor in the calendar window."
  t)

(defun generate-calendar-window (&optional mon yr)
  "Generate the calendar window for the current date.
Or, for optional MON, YR."
  (let* ((buffer-read-only nil)
         (today (calendar-current-date))
         (month (extract-calendar-month today))
         (day (extract-calendar-day today))
         (year (extract-calendar-year today))
         (today-visible
          (or (not mon)
              (let ((offset (calendar-interval mon yr month year)))
                (and (<= offset 1) (>= offset -1)))))
         (day-in-week (calendar-day-of-week today)))
    (update-calendar-mode-line)
    (if mon
        (generate-calendar mon yr)
        (generate-calendar month year))
    (calendar-cursor-to-visible-date
     (if today-visible today (list displayed-month 1 displayed-year)))
    (set-buffer-modified-p nil)
    (if (or (one-window-p t) (/= (frame-width) (window-width)))
	;; Don't mess with the window size, but ensure that the first
	;; line is fully visible
	(set-window-vscroll nil 0)
      ;; Adjust the window to exactly fit the displayed calendar
      (fit-window-to-buffer))
    (sit-for 0)
    (if (and (boundp 'font-lock-mode)
	     font-lock-mode)
	(font-lock-fontify-buffer))
    (and mark-holidays-in-calendar
;;;         (calendar-date-is-legal-p today) ; useful for BC dates
         (mark-calendar-holidays)
         (sit-for 0))
    (unwind-protect
        (if mark-diary-entries-in-calendar (mark-diary-entries))
      (if today-visible
          (run-hooks 'today-visible-calendar-hook)
        (run-hooks 'today-invisible-calendar-hook)))))

(defun generate-calendar (month year)
  "Generate a three-month Gregorian calendar centered around MONTH, YEAR."
;;; A negative YEAR is interpreted as BC; -1 being 1 BC, and so on.
;;; Note that while calendars for years BC could be displayed as it
;;; stands, almost all other calendar functions (eg holidays) would 
;;; at best have unpredictable results for such dates.
  (if (< (+ month (* 12 (1- year))) 2)
      (error "Months before February, 1 AD are not available"))
  (setq displayed-month month
        displayed-year year)
  (erase-buffer)
  (increment-calendar-month month year -1)
  (calendar-for-loop i from 0 to 2 do
       (generate-calendar-month month year (+ 5 (* 25 i)))
       (increment-calendar-month month year 1)))

(defun generate-calendar-month (month year indent)
  "Produce a calendar for MONTH, YEAR on the Gregorian calendar.
The calendar is inserted at the top of the buffer in which point is currently
located, but indented INDENT spaces.  The indentation is done from the first
character on the line and does not disturb the first INDENT characters on the
line."
  (let* ((blank-days;; at start of month
          (mod
           (- (calendar-day-of-week (list month 1 year))
              calendar-week-start-day)
           7))
	 (last (calendar-last-day-of-month month year)))
   (goto-char (point-min))
   (calendar-insert-indented
    (calendar-string-spread
     (list (format "%s %d" (calendar-month-name month) year)) ?  20)
    indent t)
   (calendar-insert-indented "" indent);; Go to proper spot
   ;; Use the first two characters of each day to head the columns.
   (calendar-for-loop i from 0 to 6 do
      (insert
       (let ((string
              (calendar-day-name (mod (+ calendar-week-start-day i) 7) nil t)))
         (if enable-multibyte-characters
             (truncate-string-to-width string 2)
           (substring string 0 2)))
       " "))
   (calendar-insert-indented "" 0 t);; Force onto following line
   (calendar-insert-indented "" indent);; Go to proper spot
   ;; Add blank days before the first of the month
   (calendar-for-loop i from 1 to blank-days do (insert "   "))
   ;; Put in the days of the month
   (calendar-for-loop i from 1 to last do
      (insert (format "%2d " i))
      (add-text-properties
       (- (point) 3) (1- (point))
       '(mouse-face highlight
	 help-echo "mouse-2: menu of operations for this date"))
      (and (zerop (mod (+ i blank-days) 7))
           (/= i last)
           (calendar-insert-indented "" 0 t)    ;; Force onto following line
           (calendar-insert-indented "" indent)))));; Go to proper spot

(defun calendar-insert-indented (string indent &optional newline)
  "Insert STRING at column INDENT.
If the optional parameter NEWLINE is t, leave point at start of next line,
inserting a newline if there was no next line; otherwise, leave point after
the inserted text.  Value is always t."
  ;; Try to move to that column.
  (move-to-column indent)
  ;; If line is too short, indent out to that column.
  (if (< (current-column) indent)
      (indent-to indent))
  (insert string)
  ;; Advance to next line, if requested.
  (if newline
      (progn
	(end-of-line)
	(if (eobp)
            (newline)
	  (forward-line 1))))
  t)

(defun redraw-calendar ()
  "Redraw the calendar display."
  (interactive)
  (let ((cursor-date (calendar-cursor-to-nearest-date)))
    (generate-calendar-window displayed-month displayed-year)
    (calendar-cursor-to-visible-date cursor-date)))

(defcustom calendar-debug-sexp nil
  "*Turn debugging on when evaluating a sexp in the diary or holiday list."
  :type 'boolean
  :group 'calendar)

(defvar calendar-mode-map nil)
(if calendar-mode-map
    nil
  (setq calendar-mode-map (make-sparse-keymap))
  (require 'cal-menu)
  (calendar-for-loop i from 0 to 9 do
       (define-key calendar-mode-map (int-to-string i) 'digit-argument))
  (let ((l (list 'narrow-to-region 'mark-word 'mark-sexp 'mark-paragraph
                 'mark-defun 'mark-whole-buffer 'mark-page
                 'downcase-region 'upcase-region 'kill-region
                 'copy-region-as-kill 'capitalize-region 'write-region)))
    (while l
      (substitute-key-definition (car l) 'calendar-not-implemented
				 calendar-mode-map global-map)
      (setq l (cdr l))))
  (define-key calendar-mode-map "-"     'negative-argument)
  (define-key calendar-mode-map "\C-x>" 'scroll-calendar-right)
  (define-key calendar-mode-map [prior] 'scroll-calendar-right-three-months)
  (define-key calendar-mode-map "\ev"   'scroll-calendar-right-three-months)
  (define-key calendar-mode-map "\C-x<" 'scroll-calendar-left)
  (define-key calendar-mode-map [next]  'scroll-calendar-left-three-months)
  (define-key calendar-mode-map "\C-v"  'scroll-calendar-left-three-months)
  (define-key calendar-mode-map "\C-b"  'calendar-backward-day)
  (define-key calendar-mode-map "\C-p"  'calendar-backward-week)
  (define-key calendar-mode-map "\e{"   'calendar-backward-month)
  (define-key calendar-mode-map "\C-x[" 'calendar-backward-year)
  (define-key calendar-mode-map "\C-f"  'calendar-forward-day)
  (define-key calendar-mode-map "\C-n"  'calendar-forward-week)
  (define-key calendar-mode-map [left]  'calendar-backward-day)
  (define-key calendar-mode-map [up]    'calendar-backward-week)
  (define-key calendar-mode-map [right] 'calendar-forward-day)
  (define-key calendar-mode-map [down]  'calendar-forward-week)
  (define-key calendar-mode-map "\e}"   'calendar-forward-month)
  (define-key calendar-mode-map "\C-x]" 'calendar-forward-year)
  (define-key calendar-mode-map "\C-a"  'calendar-beginning-of-week)
  (define-key calendar-mode-map "\C-e"  'calendar-end-of-week)
  (define-key calendar-mode-map "\ea"   'calendar-beginning-of-month)
  (define-key calendar-mode-map "\ee"   'calendar-end-of-month)
  (define-key calendar-mode-map "\e<"   'calendar-beginning-of-year)
  (define-key calendar-mode-map "\e>"   'calendar-end-of-year)
  (define-key calendar-mode-map "\C-@"  'calendar-set-mark)
  ;; Many people are used to typing C-SPC and getting C-@.
  (define-key calendar-mode-map [?\C- ] 'calendar-set-mark)
  (define-key calendar-mode-map "\C-x\C-x" 'calendar-exchange-point-and-mark)
  (define-key calendar-mode-map "\e=" 'calendar-count-days-region)
  (define-key calendar-mode-map "gd"  'calendar-goto-date)
  (define-key calendar-mode-map "gD"  'calendar-goto-day-of-year)
  (define-key calendar-mode-map "gj"  'calendar-goto-julian-date)
  (define-key calendar-mode-map "ga"  'calendar-goto-astro-day-number)
  (define-key calendar-mode-map "gh"  'calendar-goto-hebrew-date)
  (define-key calendar-mode-map "gi"  'calendar-goto-islamic-date)
  (define-key calendar-mode-map "gb"  'calendar-goto-bahai-date)
  (define-key calendar-mode-map "gC"  'calendar-goto-chinese-date)
  (define-key calendar-mode-map "gk"  'calendar-goto-coptic-date)
  (define-key calendar-mode-map "ge"  'calendar-goto-ethiopic-date)
  (define-key calendar-mode-map "gp"  'calendar-goto-persian-date)
  (define-key calendar-mode-map "gc"  'calendar-goto-iso-date)
  (define-key calendar-mode-map "gf"  'calendar-goto-french-date)
  (define-key calendar-mode-map "gml"  'calendar-goto-mayan-long-count-date)
  (define-key calendar-mode-map "gmpc" 'calendar-previous-calendar-round-date)
  (define-key calendar-mode-map "gmnc" 'calendar-next-calendar-round-date)
  (define-key calendar-mode-map "gmph" 'calendar-previous-haab-date)
  (define-key calendar-mode-map "gmnh" 'calendar-next-haab-date)
  (define-key calendar-mode-map "gmpt" 'calendar-previous-tzolkin-date)
  (define-key calendar-mode-map "gmnt" 'calendar-next-tzolkin-date)
  (define-key calendar-mode-map "Aa"   'appt-add)
  (define-key calendar-mode-map "Ad"   'appt-delete)
  (define-key calendar-mode-map "S"   'calendar-sunrise-sunset)
  (define-key calendar-mode-map "M"   'calendar-phases-of-moon)
  (define-key calendar-mode-map " "   'scroll-other-window)
  (define-key calendar-mode-map "\C-c\C-l" 'redraw-calendar)
  (define-key calendar-mode-map "."   'calendar-goto-today)
  (define-key calendar-mode-map "o"   'calendar-other-month)
  (define-key calendar-mode-map "q"   'exit-calendar)
  (define-key calendar-mode-map "a"   'list-calendar-holidays)
  (define-key calendar-mode-map "h"   'calendar-cursor-holidays)
  (define-key calendar-mode-map "x"   'mark-calendar-holidays)
  (define-key calendar-mode-map "u"   'calendar-unmark)
  (define-key calendar-mode-map "m"   'mark-diary-entries)
  (define-key calendar-mode-map "d"   'view-diary-entries)
  (define-key calendar-mode-map "D"   'view-other-diary-entries)
  (define-key calendar-mode-map "s"   'show-all-diary-entries)
  (define-key calendar-mode-map "pd"  'calendar-print-day-of-year)
  (define-key calendar-mode-map "pC"  'calendar-print-chinese-date)
  (define-key calendar-mode-map "pk"  'calendar-print-coptic-date)
  (define-key calendar-mode-map "pe"  'calendar-print-ethiopic-date)
  (define-key calendar-mode-map "pp"  'calendar-print-persian-date)
  (define-key calendar-mode-map "pc"  'calendar-print-iso-date)
  (define-key calendar-mode-map "pj"  'calendar-print-julian-date)
  (define-key calendar-mode-map "pa"  'calendar-print-astro-day-number)
  (define-key calendar-mode-map "ph"  'calendar-print-hebrew-date)
  (define-key calendar-mode-map "pi"  'calendar-print-islamic-date)
  (define-key calendar-mode-map "pb"  'calendar-print-bahai-date)
  (define-key calendar-mode-map "pf"  'calendar-print-french-date)
  (define-key calendar-mode-map "pm"  'calendar-print-mayan-date)
  (define-key calendar-mode-map "po"  'calendar-print-other-dates)
  (define-key calendar-mode-map "id"  'insert-diary-entry)
  (define-key calendar-mode-map "iw"  'insert-weekly-diary-entry)
  (define-key calendar-mode-map "im"  'insert-monthly-diary-entry)
  (define-key calendar-mode-map "iy"  'insert-yearly-diary-entry)
  (define-key calendar-mode-map "ia"  'insert-anniversary-diary-entry)
  (define-key calendar-mode-map "ib"  'insert-block-diary-entry)
  (define-key calendar-mode-map "ic"  'insert-cyclic-diary-entry)
  (define-key calendar-mode-map "ihd" 'insert-hebrew-diary-entry)
  (define-key calendar-mode-map "ihm" 'insert-monthly-hebrew-diary-entry)
  (define-key calendar-mode-map "ihy" 'insert-yearly-hebrew-diary-entry)
  (define-key calendar-mode-map "iid" 'insert-islamic-diary-entry)
  (define-key calendar-mode-map "iim" 'insert-monthly-islamic-diary-entry)
  (define-key calendar-mode-map "iiy" 'insert-yearly-islamic-diary-entry)
  (define-key calendar-mode-map "iBd" 'insert-bahai-diary-entry)
  (define-key calendar-mode-map "iBm" 'insert-monthly-bahai-diary-entry)
  (define-key calendar-mode-map "iBy" 'insert-yearly-bahai-diary-entry)
  (define-key calendar-mode-map "?"   'calendar-goto-info-node)
  (define-key calendar-mode-map "tm" 'cal-tex-cursor-month)
  (define-key calendar-mode-map "tM" 'cal-tex-cursor-month-landscape)
  (define-key calendar-mode-map "td" 'cal-tex-cursor-day)
  (define-key calendar-mode-map "tw1" 'cal-tex-cursor-week)
  (define-key calendar-mode-map "tw2" 'cal-tex-cursor-week2)
  (define-key calendar-mode-map "tw3" 'cal-tex-cursor-week-iso)
  (define-key calendar-mode-map "tw4" 'cal-tex-cursor-week-monday)
  (define-key calendar-mode-map "tfd" 'cal-tex-cursor-filofax-daily)
  (define-key calendar-mode-map "tfw" 'cal-tex-cursor-filofax-2week)
  (define-key calendar-mode-map "tfW" 'cal-tex-cursor-filofax-week)
  (define-key calendar-mode-map "tfy" 'cal-tex-cursor-filofax-year)
  (define-key calendar-mode-map "ty" 'cal-tex-cursor-year)
  (define-key calendar-mode-map "tY" 'cal-tex-cursor-year-landscape))

(defun describe-calendar-mode ()
  "Create a help buffer with a brief description of the `calendar-mode'."
  (interactive)
  (with-output-to-temp-buffer "*Help*"
    (princ
     (format
      "Calendar Mode:\nFor a complete description, type %s\n%s\n"
      (substitute-command-keys
       "\\<calendar-mode-map>\\[describe-mode] from within the calendar")
      (substitute-command-keys "\\{calendar-mode-map}")))
    (save-excursion
      (set-buffer standard-output)
      (help-mode))
    (print-help-return-message)))

;; Calendar mode is suitable only for specially formatted data.
(put 'calendar-mode 'mode-class 'special)

(defvar calendar-mode-line-format
  (list
   (propertize (substitute-command-keys
		"\\<calendar-mode-map>\\[scroll-calendar-left]")
	       'help-echo "mouse-2: scroll left"
	       'keymap (make-mode-line-mouse-map 'mouse-2
						 'mouse-scroll-calendar-left))
   "Calendar"
   (concat
    (propertize
     (substitute-command-keys
      "\\<calendar-mode-map>\\[calendar-goto-info-node] info")
     'help-echo "mouse-2: read Info on Calendar"
     'keymap (make-mode-line-mouse-map 'mouse-2 'calendar-goto-info-node))
    "/"
    (propertize
     (substitute-command-keys
     "\\<calendar-mode-map>\\[calendar-other-month] other")
     'help-echo "mouse-2: choose another month"
     'keymap (make-mode-line-mouse-map
	      'mouse-2 'mouse-calendar-other-month))
    "/"
    (propertize
     (substitute-command-keys
     "\\<calendar-mode-map>\\[calendar-goto-today] today")
     'help-echo "mouse-2: go to today's date"
     'keymap (make-mode-line-mouse-map 'mouse-2 #'calendar-goto-today)))
   '(calendar-date-string (calendar-current-date) t)
   (propertize (substitute-command-keys
		"\\<calendar-mode-map>\\[scroll-calendar-right]")
	       'help-echo "mouse-2: scroll right"
	       'keymap (make-mode-line-mouse-map
			'mouse-2 'mouse-scroll-calendar-right)))
  "The mode line of the calendar buffer.

This must be a list of items that evaluate to strings--those strings are
evaluated and concatenated together, evenly separated by blanks.  The variable
`date' is available for use as the date under (or near) the cursor; `date'
defaults to the current date if it is otherwise undefined.  Here is an example
value that has the Hebrew date, the day number/days remaining in the year,
and the ISO week/year numbers in the mode.  When calendar-move-hook is set to
'update-calendar-mode-line, these mode line shows these values for the date
under the cursor:

      (list
       \"\"
       '(calendar-hebrew-date-string date)
       '(let* ((year (extract-calendar-year date))
               (d (calendar-day-number date))
               (days-remaining
                (- (calendar-day-number (list 12 31 year)) d)))
          (format \"%d/%d\" d days-remaining))
       '(let* ((d (calendar-absolute-from-gregorian date))
               (iso-date (calendar-iso-from-absolute d)))
          (format \"ISO week %d of %d\"
            (extract-calendar-month iso-date)
            (extract-calendar-year iso-date)))
       \"\"))
")

(defun mouse-scroll-calendar-left (event)
  "Scroll the displayed calendar left by one month.
Maintains the relative position of the cursor
with respect to the calendar as well as possible."
  (interactive "e")
  (save-selected-window
    (select-window (posn-window (event-start event)))
    (scroll-calendar-left 1)))

(defun mouse-scroll-calendar-right (event)
  "Scroll the displayed calendar right by one month.
Maintains the relative position of the cursor
with respect to the calendar as well as possible."
  (interactive "e")
  (save-selected-window
    (select-window (posn-window (event-start event)))
    (scroll-calendar-right 1)))

(defun mouse-calendar-other-month (event)
  "Display a three-month calendar centered around a specified month and year."
  (interactive "e")
  (save-selected-window
    (select-window (posn-window (event-start event)))
    (call-interactively 'calendar-other-month)))

(defun calendar-goto-info-node ()
  "Go to the info node for the calendar."
  (interactive)
  (require 'info)
  (let ((where (save-window-excursion
		 (Info-find-emacs-command-nodes 'calendar))))
    (if (not where)
        (error "Couldn't find documentation for the calendar")
      (let (same-window-buffer-names)
	(info))
      (Info-find-node (car (car where)) (car (cdr (car where)))))))


(defun calendar-mode ()
  "A major mode for the calendar window.

For a complete description, type \
\\<calendar-mode-map>\\[calendar-goto-info-node] from within the calendar.

\\<calendar-mode-map>\\{calendar-mode-map}"

  (kill-all-local-variables)
  (setq major-mode 'calendar-mode)
  (setq mode-name "Calendar")
  (use-local-map calendar-mode-map)
  (setq buffer-read-only t)
  (setq indent-tabs-mode nil)
  (update-calendar-mode-line)
  (add-hook 'activate-menubar-hook 'cal-menu-update nil t)
  (make-local-variable 'calendar-mark-ring)
  (make-local-variable 'displayed-month);;  Month in middle of window.
  (make-local-variable 'displayed-year)	;;  Year in middle of window.
  (set (make-local-variable 'font-lock-defaults)
       '(calendar-font-lock-keywords t)))

(defun calendar-string-spread (strings char length)
  "Concatenate list of STRINGS separated with copies of CHAR to fill LENGTH.
The effect is like mapconcat but the separating pieces are as balanced as
possible.  Each item of STRINGS is evaluated before concatenation so it can
actually be an expression that evaluates to a string.  If LENGTH is too short,
the STRINGS are just concatenated and the result truncated."
;; The algorithm is based on equation (3.25) on page 85 of Concrete
;; Mathematics by Ronald L. Graham, Donald E. Knuth, and Oren Patashnik,
;; Addison-Wesley, Reading, MA, 1989
  (let* ((strings (mapcar 'eval
                          (if (< (length strings) 2)
                              (append (list "") strings (list ""))
                            strings)))
         (n (- length (length (apply 'concat strings))))
         (m (1- (length strings)))
         (s (car strings))
         (strings (cdr strings))
         (i 0))
    (while strings
      (setq s (concat s
                      (make-string (max 0 (/ (+ n i) m)) char)
                      (car strings)))
      (setq i (1+ i))
      (setq strings (cdr strings)))
    (substring s 0 length)))

(defun update-calendar-mode-line ()
  "Update the calendar mode line with the current date and date style."
  (if (bufferp (get-buffer calendar-buffer))
      (save-excursion
        (set-buffer calendar-buffer)
        (setq mode-line-format
              (calendar-string-spread
               (let ((date (condition-case nil
                               (calendar-cursor-to-nearest-date)
                             (error (calendar-current-date)))))
                 (mapcar 'eval  calendar-mode-line-format))
               ?  (frame-width)))
        (force-mode-line-update))))

(defun calendar-window-list ()
  "List of all calendar-related windows."
  (let ((calendar-buffers (calendar-buffer-list))
        list)
    (walk-windows (lambda (w)
		    (if (memq (window-buffer w) calendar-buffers)
			(setq list (cons w list))))
                  nil t)
    list))

(defun calendar-buffer-list ()
  "List of all calendar-related buffers."
  (let* ((diary-buffer (get-file-buffer diary-file))
         (buffers (list "*Yahrzeits*" lunar-phases-buffer holiday-buffer
                        fancy-diary-buffer diary-buffer calendar-buffer
                        other-calendars-buffer))
         (buffer-list nil)
         b)
    (while buffers
      (setq b (car buffers))
      (setq b (cond ((stringp b) (get-buffer b))
                    ((bufferp b) b)
                    (t nil)))
      (if b (setq buffer-list (cons b buffer-list)))
      (setq buffers (cdr buffers)))
    buffer-list))

(defun exit-calendar ()
  "Get out of the calendar window and hide it and related buffers."
  (interactive)
  (let* ((diary-buffer (get-file-buffer diary-file)))
    (if (or (not diary-buffer)
            (not (buffer-modified-p diary-buffer))
            (yes-or-no-p
             "Diary modified; do you really want to exit the calendar? "))
      ;; Need to do this multiple times because one time can replace some
      ;; calendar-related buffers with other calendar-related buffers
      (mapcar (lambda (x)
                (mapcar 'calendar-hide-window (calendar-window-list)))
              (calendar-window-list)))))

(defun calendar-hide-window (window)
  "Hide WINDOW if it is calendar-related."
  (let ((buffer (if (window-live-p window) (window-buffer window))))
    (if (memq buffer (calendar-buffer-list))
        (cond
         ((and (display-multi-frame-p)
               (eq 'icon (cdr (assoc 'visibility
                                     (frame-parameters
                                      (window-frame window))))))
          nil)
         ((and (display-multi-frame-p) (window-dedicated-p window))
          (if calendar-remove-frame-by-deleting
              (delete-frame (window-frame window))
              (iconify-frame (window-frame window))))
         ((not (and (select-window window) (one-window-p window)))
          (delete-window window))
         (t (set-buffer buffer)
            (bury-buffer))))))

(defun calendar-current-date ()
  "Return the current date in a list (month day year)."
  (let ((now (decode-time)))
    (list (nth 4 now) (nth 3 now) (nth 5 now))))

(defun calendar-cursor-to-date (&optional error)
  "Return a list (month day year) of current cursor position.
If cursor is not on a specific date, signals an error if optional parameter
ERROR is t, otherwise just returns nil."
  (let* ((segment (/ (current-column) 25))
         (month (% (+ displayed-month segment -1) 12))
         (month (if (= 0 month) 12 month))
         (year
          (cond
           ((and (=  12 month) (= segment 0)) (1- displayed-year))
           ((and (=   1 month) (= segment 2)) (1+ displayed-year))
           (t displayed-year))))
    (if (and (looking-at "[ 0-9]?[0-9][^0-9]")
             (< 2 (count-lines (point-min) (point))))
        (save-excursion
          (if (not (looking-at " "))
                   (re-search-backward "[^0-9]"))
          (list month
                (string-to-int (buffer-substring (1+ (point)) (+ 4 (point))))
                year))
      (if (looking-at "\\*")
          (save-excursion
            (re-search-backward "[^*]")
            (if (looking-at ".\\*\\*")
                (list month calendar-starred-day year)
              (if error (error "Not on a date!"))))
        (if error (error "Not on a date!"))))))

;; The following version of calendar-gregorian-from-absolute is preferred for
;; reasons of clarity, BUT it's much slower than the version that follows it.

;;(defun calendar-gregorian-from-absolute (date)
;;  "Compute the list (month day year) corresponding to the absolute DATE.
;;The absolute date is the number of days elapsed since the (imaginary)
;;Gregorian date Sunday, December 31, 1 BC."
;;  (let* ((approx (/ date 366));; Approximation from below.
;;         (year                ;; Search forward from the approximation.
;;          (+ approx
;;             (calendar-sum y approx
;;                 (>= date (calendar-absolute-from-gregorian (list 1 1 (1+ y))))
;;                  1)))
;;         (month         ;; Search forward from January.
;;          (1+ (calendar-sum m 1
;;                   (> date
;;                      (calendar-absolute-from-gregorian
;;                       (list m (calendar-last-day-of-month m year) year)))
;;                   1)))
;;         (day           ;; Calculate the day by subtraction.
;;          (- date
;;             (1- (calendar-absolute-from-gregorian (list month 1 year))))))
;;    (list month day year)))

(defun calendar-gregorian-from-absolute (date)
  "Compute the list (month day year) corresponding to the absolute DATE.
The absolute date is the number of days elapsed since the (imaginary)
Gregorian date Sunday, December 31, 1 BC.  This function does not
handle dates in years BC."
;; See the footnote on page 384 of ``Calendrical Calculations, Part II:
;; Three Historical Calendars'' by E. M. Reingold,  N. Dershowitz, and S. M.
;; Clamen, Software--Practice and Experience, Volume 23, Number 4
;; (April, 1993), pages 383-404 for an explanation.
  (let* ((d0 (1- date))
         (n400 (/ d0 146097))
         (d1 (% d0 146097))
         (n100 (/ d1 36524))
         (d2 (% d1 36524))
         (n4 (/ d2 1461))
         (d3 (% d2 1461))
         (n1 (/ d3 365))
         (day (1+ (% d3 365)))
         (year (+ (* 400 n400) (* 100 n100) (* n4 4) n1)))
    (if (or (= n100 4) (= n1 4))
        (list 12 31 year)
      (let ((year (1+ year))
            (month 1))
        (while (let ((mdays (calendar-last-day-of-month month year)))
                 (and (< mdays day)
                      (setq day (- day mdays))))
          (setq month (1+ month)))
        (list month day year)))))

(defun calendar-other-month (month year)
  "Display a three-month calendar centered around MONTH and YEAR."
  (interactive (calendar-read-date 'noday))
  (if (and (= month displayed-month)
           (= year displayed-year))
      nil
    (let ((old-date (calendar-cursor-to-date))
          (today (calendar-current-date)))
      (generate-calendar-window month year)
      (calendar-cursor-to-visible-date
       (cond
        ((calendar-date-is-visible-p old-date) old-date)
        ((calendar-date-is-visible-p today) today)
        (t (list month 1 year)))))))

(defun calendar-set-mark (arg)
  "Mark the date under the cursor, or jump to marked date.
With no prefix argument, push current date onto marked date ring.
With argument, jump to mark, pop it, and put point at end of ring."
  (interactive "P")
  (let ((date (calendar-cursor-to-date t)))
    (if (null arg)
        (progn
          (setq calendar-mark-ring (cons date calendar-mark-ring))
          ;; Since the top of the mark ring is the marked date in the
          ;; calendar, the mark ring in the calendar is one longer than
          ;; in other buffers to get the same effect.
          (if (> (length calendar-mark-ring) (1+ mark-ring-max))
              (setcdr (nthcdr mark-ring-max calendar-mark-ring) nil))
          (message "Mark set"))
      (if (null calendar-mark-ring)
          (error "No mark set in this buffer")
        (calendar-goto-date (car calendar-mark-ring))
        (setq calendar-mark-ring
              (cdr (nconc calendar-mark-ring (list date))))))))

(defun calendar-exchange-point-and-mark ()
  "Exchange the current cursor position with the marked date."
  (interactive)
  (let ((mark (car calendar-mark-ring))
        (date (calendar-cursor-to-date t)))
    (if (null mark)
        (error "No mark set in this buffer")
      (setq calendar-mark-ring (cons date (cdr calendar-mark-ring)))
      (calendar-goto-date mark))))

(defun calendar-count-days-region ()
  "Count the number of days (inclusive) between point and the mark."
  (interactive)
  (let* ((days (- (calendar-absolute-from-gregorian
                   (calendar-cursor-to-date t))
                  (calendar-absolute-from-gregorian
                   (or (car calendar-mark-ring)
                       (error "No mark set in this buffer")))))
         (days (1+ (if (> days 0) days (- days)))))
    (message "Region has %d day%s (inclusive)"
             days (if (> days 1) "s" ""))))

(defun calendar-not-implemented ()
  "Not implemented."
  (interactive)
  (error "%s not available in the calendar"
         (global-key-binding (this-command-keys))))

(defun calendar-read (prompt acceptable &optional initial-contents)
  "Return an object read from the minibuffer.
Prompt with the string PROMPT and use the function ACCEPTABLE to decide if
entered item is acceptable.  If non-nil, optional third arg INITIAL-CONTENTS
is a string to insert in the minibuffer before reading."
  (let ((value (read-minibuffer prompt initial-contents)))
    (while (not (funcall acceptable value))
      (setq value (read-minibuffer prompt initial-contents)))
    value))

(defun calendar-read-date (&optional noday)
  "Prompt for Gregorian date.  Return a list (month day year).
If optional NODAY is t, does not ask for day, but just returns
\(month nil year); if NODAY is any other non-nil value the value returned is
\(month year)"
  (let* ((year (calendar-read
                "Year (>0): "
                (lambda (x) (> x 0))
                (int-to-string (extract-calendar-year
                                (calendar-current-date)))))
         (month-array calendar-month-name-array)
         (completion-ignore-case t)
         (month (cdr (assoc-string
                       (completing-read
                        "Month name: "
                        (mapcar 'list (append month-array nil))
                        nil t)
                      (calendar-make-alist month-array 1) t)))
         (last (calendar-last-day-of-month month year)))
    (if noday
        (if (eq noday t)
            (list month nil year)
          (list month year))
      (list month
            (calendar-read (format "Day (1-%d): " last)
			   (lambda (x) (and (< 0 x) (<= x last))))
            year))))

(defun calendar-interval (mon1 yr1 mon2 yr2)
  "The number of months difference between MON1, YR1 and MON2, YR2.
The result is positive if the second date is later than the first.
Negative years are interpreted as years BC; -1 being 1 BC, and so on."
  (if (< yr1 0) (setq yr1 (1+ yr1)))      ; -1 BC -> 0 AD, etc
  (if (< yr2 0) (setq yr2 (1+ yr2)))
  (+ (* 12 (- yr2 yr1))
     (- mon2 mon1)))

(defvar calendar-abbrev-length 3
  "*Length of abbreviations to be used for day and month names.
See also `calendar-day-abbrev-array' and `calendar-month-abbrev-array'.")

(defvar calendar-day-name-array
  ["Sunday" "Monday" "Tuesday" "Wednesday" "Thursday" "Friday" "Saturday"]
  "*Array of capitalized strings giving, in order, the day names.
The first two characters of each string will be used to head the
day columns in the calendar.  See also the variable
`calendar-day-abbrev-array'.")

(defvar calendar-day-abbrev-array
  [nil nil nil nil nil nil nil]
  "*Array of capitalized strings giving the abbreviated day names.
The order should be the same as that of the full names specified
in `calendar-day-name-array'.  These abbreviations may be used
instead of the full names in the diary file.  Do not include a
trailing `.' in the strings specified in this variable, though
you may use such in the diary file.  If any element of this array
is nil, then the abbreviation will be constructed as the first 
`calendar-abbrev-length' characters of the corresponding full name.")

(defvar calendar-month-name-array
  ["January" "February" "March"     "April"   "May"      "June"
   "July"    "August"   "September" "October" "November" "December"]
  "*Array of capitalized strings giving, in order, the month names.
See also the variable `calendar-month-abbrev-array'.")

(defvar calendar-month-abbrev-array
  [nil nil nil nil nil nil nil nil nil nil nil nil]
 "*Array of capitalized strings giving the abbreviated month names.
The order should be the same as that of the full names specified
in `calendar-month-name-array'.  These abbreviations are used in
the calendar menu entries, and can also be used in the diary
file.  Do not include a trailing `.' in the strings specified in
this variable, though you may use such in the diary file.  If any
element of this array is nil, then the abbreviation will be
constructed as the first `calendar-abbrev-length' characters of the
corresponding full name.")

(defun calendar-abbrev-construct (abbrev full &optional period)
  "Internal calendar function to return a complete abbreviation array.
ABBREV is an array of abbreviations, FULL the corresponding array
of full names.  The return value is the ABBREV array, with any nil
elements replaced by the first three characters taken from the
corresponding element of FULL.  If optional argument PERIOD is non-nil,
each element returned has a final `.' character."
  (let (elem array name)
    (dotimes (i (length full))
      (setq name (aref full i)
            elem (or (aref abbrev i)
                     (substring name 0
                                (min calendar-abbrev-length (length name))))
            elem (format "%s%s" elem (if period "." ""))
            array (append array (list elem))))
    (vconcat array)))

(defvar calendar-font-lock-keywords
  `((,(concat (regexp-opt (mapcar 'identity calendar-month-name-array) t)
	      " -?[0-9]+")
     . font-lock-function-name-face) ; month and year
    (,(regexp-opt
       (list (substring (aref calendar-day-name-array 6) 0 2)
	     (substring (aref calendar-day-name-array 0) 0 2)))
     ;; Saturdays and Sundays are hilited differently.
     . font-lock-comment-face)
    ;; First two chars of each day are used in the calendar.
    (,(regexp-opt (mapcar (lambda (x) (substring x 0 2)) calendar-day-name-array))
     . font-lock-reference-face))
  "Default keywords to highlight in Calendar mode.")

(defun calendar-day-name (date &optional abbrev absolute)
  "Return a string with the name of the day of the week of DATE.
DATE should be a list in the format (MONTH DAY YEAR), unless the
optional argument ABSOLUTE is non-nil, in which case DATE should
be an integer in the range 0 to 6 corresponding to the day of the
week.  Day names are taken from the variable `calendar-day-name-array',
unless the optional argument ABBREV is non-nil, in which case
the variable `calendar-day-abbrev-array' is used."
  (aref (if abbrev
            (calendar-abbrev-construct calendar-day-abbrev-array
                                       calendar-day-name-array)
          calendar-day-name-array)
        (if absolute date (calendar-day-of-week date))))

(defun calendar-make-alist (sequence &optional start-index filter abbrevs)
  "Make an assoc list corresponding to SEQUENCE.
Each element of sequence will be associated with an integer, starting
from 1, or from START-INDEX if that is non-nil.  If a sequence ABBREVS
is supplied, the function `calendar-abbrev-construct' is used to
construct abbreviations corresponding to the elements in SEQUENCE.
Each abbreviation is entered into the alist with the same
association index as the full name it represents.
If FILTER is provided, apply it to each key in the alist."
  (let ((index 0)
        (offset (or start-index 1))
        (aseq (if abbrevs (calendar-abbrev-construct abbrevs sequence)))
        (aseqp (if abbrevs (calendar-abbrev-construct abbrevs sequence
                                                      'period)))
        alist elem)
    (dotimes (i (length sequence) (reverse alist))
      (setq index (+ i offset)
            elem (elt sequence i)
            alist
            (cons (cons (if filter (funcall filter elem) elem) index) alist))
      (if aseq
          (setq elem (elt aseq i)
                alist (cons (cons (if filter (funcall filter elem) elem)
                                  index) alist)))
      (if aseqp
          (setq elem (elt aseqp i)
                alist (cons (cons (if filter (funcall filter elem) elem)
                                  index) alist))))))

(defun calendar-month-name (month &optional abbrev)
  "Return a string with the name of month number MONTH.
Months are numbered from one.  Month names are taken from the
variable `calendar-month-name-array', unless the optional
argument ABBREV is non-nil, in which case
`calendar-month-abbrev-array' is used."
  (aref (if abbrev
            (calendar-abbrev-construct calendar-month-abbrev-array
                                       calendar-month-name-array)
          calendar-month-name-array)
        (1- month)))

(defun calendar-day-of-week (date)
  "Return the day-of-the-week index of DATE, 0 for Sunday, 1 for Monday, etc.
DATE is a list of the form (month day year).  A negative year is
interpreted as BC; -1 being 1 BC, and so on."
  (mod (calendar-absolute-from-gregorian date) 7))

(defun calendar-unmark ()
  "Delete all diary/holiday marks/highlighting from the calendar."
  (interactive)
  (setq mark-holidays-in-calendar nil)
  (setq mark-diary-entries-in-calendar nil)
  (redraw-calendar))

(defun calendar-date-is-visible-p (date)
  "Return t if DATE is legal and is visible in the calendar window."
  (let ((gap (calendar-interval
              displayed-month displayed-year
              (extract-calendar-month date) (extract-calendar-year date))))
    (and (calendar-date-is-legal-p date) (> 2 gap) (< -2 gap))))

(defun calendar-date-is-legal-p (date)
  "Return t if DATE is a legal date."
  (let ((month (extract-calendar-month date))
        (day (extract-calendar-day date))
        (year (extract-calendar-year date)))
    (and (<= 1 month) (<= month 12)
         (<= 1 day) (<= day (calendar-last-day-of-month month year))
         ;; BC dates left as non-legal, to suppress errors from
         ;; complex holiday algorithms not suitable for years BC.
         ;; Note there are side effects on calendar navigation.
         (<= 1 year))))

(defun calendar-date-equal (date1 date2)
  "Return t if the DATE1 and DATE2 are the same."
  (and
   (= (extract-calendar-month date1) (extract-calendar-month date2))
   (= (extract-calendar-day date1) (extract-calendar-day date2))
   (= (extract-calendar-year date1) (extract-calendar-year date2))))

(defun mark-visible-calendar-date (date &optional mark)
  "Mark DATE in the calendar window with MARK.
MARK is a single-character string, a list of face attributes/values, or a face.
MARK defaults to `diary-entry-marker'."
  (if (calendar-date-is-legal-p date)
      (save-excursion
        (set-buffer calendar-buffer)
        (calendar-cursor-to-visible-date date)
	(let ((mark (or (and (stringp mark) (= (length mark) 1) mark) ; single-char
			(and (listp mark) (> (length mark) 0) mark) ; attr list
			(and (facep mark) mark) ; face-name
			diary-entry-marker)))
	  (if (facep mark)
	      (progn ; face or an attr-list that contained a face
		(overlay-put
		 (make-overlay (1- (point)) (1+ (point))) 'face mark))
	    (if (and (stringp mark)
		     (= (length mark) 1)) ; single-char
		(let ((buffer-read-only nil))
		  (forward-char 1)
		  (delete-char 1)
		  (insert mark)
		  (forward-char -2))
              (let ; attr list 
                  ((temp-face 
                    (make-symbol (apply 'concat "temp-face-" 
                                        (mapcar '(lambda (sym) 
                                                   (cond ((symbolp sym) (symbol-name sym))
                                                         ((numberp sym) (int-to-string sym))
                                                         (t sym))) mark))))
                   (faceinfo mark))
		(make-face temp-face)
		;; Remove :face info from the mark, copy the face info into temp-face
		(while (setq faceinfo (memq :face faceinfo))
		  (copy-face (read (nth 1 faceinfo)) temp-face)
		  (setcar faceinfo nil)
		  (setcar (cdr faceinfo) nil))
		(setq mark (delq nil mark))
		;; Apply the font aspects
		(apply 'set-face-attribute temp-face nil mark)
		(overlay-put
		 (make-overlay (1- (point)) (1+ (point))) 'face temp-face))))))))

(defun calendar-star-date ()
  "Replace the date under the cursor in the calendar window with asterisks.
This function can be used with the `today-visible-calendar-hook' run after the
calendar window has been prepared."
  (let ((inhibit-read-only t))
    (make-local-variable 'calendar-starred-day)
    (forward-char 1)
    (setq calendar-starred-day
          (string-to-int
           (buffer-substring (point) (- (point) 2))))
    (delete-char -2)
    (insert "**")
    (backward-char 1)
    (set-buffer-modified-p nil)))

(defun calendar-mark-today ()
  "Mark the date under the cursor in the calendar window.
The date is marked with `calendar-today-marker'.  This function can be used with
the `today-visible-calendar-hook' run after the calendar window has been
prepared."
  (mark-visible-calendar-date
   (calendar-cursor-to-date)
   calendar-today-marker))

(defun calendar-date-compare (date1 date2)
  "Return t if DATE1 is before DATE2, nil otherwise.
The actual dates are in the car of DATE1 and DATE2."
  (< (calendar-absolute-from-gregorian (car date1))
     (calendar-absolute-from-gregorian (car date2))))

(defun calendar-date-string (date &optional abbreviate nodayname)
  "A string form of DATE, driven by the variable `calendar-date-display-form'.
An optional parameter ABBREVIATE, when non-nil, causes the month
and day names to be abbreviated as specified by
`calendar-month-abbrev-array' and `calendar-day-abbrev-array',
respectively.  An optional parameter NODAYNAME, when t, omits the
name of the day of the week."
  (let* ((dayname
          (unless nodayname
            (calendar-day-name date abbreviate)))
         (month (extract-calendar-month date))
         (monthname (calendar-month-name month abbreviate))
         (day (int-to-string (extract-calendar-day date)))
         (month (int-to-string month))
         (year (int-to-string (extract-calendar-year date))))
    (mapconcat 'eval calendar-date-display-form "")))

(defun calendar-dayname-on-or-before (dayname date)
  "Return the absolute date of the DAYNAME on or before absolute DATE.
DAYNAME=0 means Sunday, DAYNAME=1 means Monday, and so on.

Note: Applying this function to d+6 gives us the DAYNAME on or after an
absolute day d.  Similarly, applying it to d+3 gives the DAYNAME nearest to
absolute date d, applying it to d-1 gives the DAYNAME previous to absolute
date d, and applying it to d+7 gives the DAYNAME following absolute date d."
  (- date (% (- date dayname) 7)))

(defun calendar-nth-named-absday (n dayname month year &optional day)
  "The absolute date of Nth DAYNAME in MONTH, YEAR before/after optional DAY.
A DAYNAME of 0 means Sunday, 1 means Monday, and so on.  If N<0,
return the Nth DAYNAME before MONTH DAY, YEAR (inclusive).
If N>0, return the Nth DAYNAME after MONTH DAY, YEAR (inclusive).

If DAY is omitted, it defaults to 1 if N>0, and MONTH's last day otherwise."
  (if (> n 0)
      (+ (* 7 (1- n))
	 (calendar-dayname-on-or-before
	  dayname
	  (+ 6 (calendar-absolute-from-gregorian
		(list month (or day 1) year)))))
    (+ (* 7 (1+ n))
       (calendar-dayname-on-or-before
	dayname
	(calendar-absolute-from-gregorian
	 (list month
	       (or day (calendar-last-day-of-month month year))
	       year))))))

(defun calendar-nth-named-day (n dayname month year &optional day)
  "The date of Nth DAYNAME in MONTH, YEAR before/after optional DAY.
A DAYNAME of 0 means Sunday, 1 means Monday, and so on.  If N<0,
return the Nth DAYNAME before MONTH DAY, YEAR (inclusive).
If N>0, return the Nth DAYNAME after MONTH DAY, YEAR (inclusive).

If DAY is omitted, it defaults to 1 if N>0, and MONTH's last day otherwise."
  (calendar-gregorian-from-absolute
   (calendar-nth-named-absday n dayname month year day)))

(defun calendar-day-of-year-string (&optional date)
  "String of day number of year of Gregorian DATE.
Defaults to today's date if DATE is not given."
  (let* ((d (or date (calendar-current-date)))
         (year (extract-calendar-year d))
         (day (calendar-day-number d))
         (days-remaining (- (calendar-day-number (list 12 31 year)) day)))
    (format "Day %d of %d; %d day%s remaining in the year"
            day year days-remaining (if (= days-remaining 1) "" "s"))))

(defun calendar-print-other-dates ()
  "Show dates on other calendars for date under the cursor."
  (interactive)
  (let* ((date (calendar-cursor-to-date t)))
    (save-excursion
      (set-buffer (get-buffer-create other-calendars-buffer))
      (setq buffer-read-only nil)
      (calendar-set-mode-line
       (concat (calendar-date-string date) " (Gregorian)"))
      (erase-buffer)
      (insert
       (mapconcat 'identity
                  (list (calendar-day-of-year-string date)
                        (format "ISO date: %s" (calendar-iso-date-string date))
                        (format "Julian date: %s"
                                (calendar-julian-date-string date))
                        (format
                         "Astronomical (Julian) day number (at noon UTC): %s.0"
                         (calendar-astro-date-string date))
                        (format "Fixed (RD) date: %s"
                                (calendar-absolute-from-gregorian date))
                        (format "Hebrew date (before sunset): %s"
                                (calendar-hebrew-date-string date))
                        (format "Persian date: %s"
                                (calendar-persian-date-string date))
                        (let ((i (calendar-islamic-date-string date)))
                          (if (not (string-equal i ""))
                              (format "Islamic date (before sunset): %s" i)))
			(let ((b (calendar-bahai-date-string date)))
			  (if (not (string-equal b ""))
			      (format "Baha'i date (before sunset): %s" b)))
                        (format "Chinese date: %s"
                                (calendar-chinese-date-string date))
                        (let ((c (calendar-coptic-date-string date)))
                          (if (not (string-equal c ""))
                              (format "Coptic date: %s" c)))
                        (let ((e (calendar-ethiopic-date-string date)))
                          (if (not (string-equal e ""))
                              (format "Ethiopic date: %s" e)))
                        (let ((f (calendar-french-date-string date)))
                          (if (not (string-equal f ""))
                              (format "French Revolutionary date: %s" f)))
                        (format "Mayan date: %s"
                                (calendar-mayan-date-string date)))
                  "\n"))
      (goto-char (point-min))
      (set-buffer-modified-p nil)
      (setq buffer-read-only t)
      (display-buffer other-calendars-buffer))))

(defun calendar-print-day-of-year ()
  "Show day number in year/days remaining in year for date under the cursor."
  (interactive)
  (message (calendar-day-of-year-string (calendar-cursor-to-date t))))

(defun calendar-set-mode-line (str)
  "Set mode line to STR, centered, surrounded by dashes."
  (setq mode-line-format
        (calendar-string-spread
         (list str) ?-
         ;; As per doc of window-width, total visible mode-line length.
         (let ((edges (window-edges))) (- (nth 2 edges) (nth 0 edges))))))

(defun calendar-mod (m n)
  "Non-negative remainder of M/N with N instead of 0."
  (1+ (mod (1- m) n)))

(run-hooks 'calendar-load-hook)

(provide 'calendar)

;;; Local variables:
;;; byte-compile-dynamic: t
;;; End:

;;; arch-tag: 19c61596-c8fb-4c69-bcf1-7dd739919cd8
;;; calendar.el ends here