[bpt/emacs.git] / lisp / calendar / cal-julian.el

;;; cal-julian.el --- calendar functions for the Julian calendar.

;; Copyright (C) 1995, 1997 Free Software Foundation, Inc.

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

;; 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 the features of calendar.el and
;; diary.el that deal with the Julian calendar.

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

;; 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:

(require 'calendar)

(defun calendar-julian-from-absolute (date)
  "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."
  (let* ((approx (/ (+ date 2) 366));; Approximation from below.
         (year        ;; Search forward from the approximation.
          (+ approx
             (calendar-sum y approx
                (>= date (calendar-absolute-from-julian (list 1 1 (1+ y))))
                1)))
         (month       ;; Search forward from January.
          (1+ (calendar-sum m 1
                 (> date
                    (calendar-absolute-from-julian
                     (list m
                           (if (and (= m 2) (= (% year 4) 0))
                               29
                             (aref [31 28 31 30 31 30 31 31 30 31 30 31]
                                   (1- m)))
                           year)))
                 1)))
         (day         ;; Calculate the day by subtraction.
          (- date (1- (calendar-absolute-from-julian (list month 1 year))))))
    (list month day year)))

(defun calendar-absolute-from-julian (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."
  (let ((month (extract-calendar-month date))
        (day (extract-calendar-day date))
        (year (extract-calendar-year date)))
    (+ (calendar-day-number date)
       (if (and (= (% year 100) 0)
                (/= (% year 400) 0)
                (> month 2))
           1 0);; Correct for Julian but not Gregorian leap year.
       (* 365 (1- year))
       (/ (1- year) 4)
       -2)))

(defun calendar-julian-date-string (&optional date)
  "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'."
  (calendar-date-string
   (calendar-julian-from-absolute
    (calendar-absolute-from-gregorian
     (or date (calendar-current-date))))
   nil t))

(defun calendar-print-julian-date ()
  "Show the Julian calendar equivalent of the date under the cursor."
  (interactive)
  (message "Julian date: %s"
           (calendar-julian-date-string (calendar-cursor-to-date t))))

(defun calendar-goto-julian-date (date &optional noecho)
  "Move cursor to Julian DATE; echo Julian date unless NOECHO is t."
  (interactive
   (let* ((today (calendar-current-date))
          (year (calendar-read
                 "Julian calendar year (>0): "
                 '(lambda (x) (> x 0))
                 (int-to-string
                  (extract-calendar-year
                   (calendar-julian-from-absolute
                    (calendar-absolute-from-gregorian
                     today))))))
          (month-array calendar-month-name-array)
          (completion-ignore-case t)
          (month (cdr (assoc-ignore-case
                        (completing-read
                         "Julian calendar month name: "
                         (mapcar 'list (append month-array nil))
                         nil t)
                       (calendar-make-alist month-array 1))))
          (last 
           (if (and (zerop (% year 4)) (= month 2))
               29
             (aref [31 28 31 30 31 30 31 31 30 31 30 31] (1- month))))
          (day (calendar-read
                (format "Julian calendar day (%d-%d): "
                        (if (and (= year 1) (= month 1)) 3 1) last)
                '(lambda (x) 
                   (and (< (if (and (= year 1) (= month 1)) 2 0) x)
                        (<= x last))))))
     (list (list month day year))))
  (calendar-goto-date (calendar-gregorian-from-absolute
                       (calendar-absolute-from-julian date)))
  (or noecho (calendar-print-julian-date)))

(defun holiday-julian (month day string)
  "Holiday on MONTH, DAY  (Julian) called STRING.
If MONTH, DAY (Julian) is visible, the value returned is corresponding
Gregorian date in the form of the list (((month day year) STRING)).  Returns
nil if it is not visible in the current calendar window."
  (let ((m1 displayed-month)
        (y1 displayed-year)
        (m2 displayed-month)
        (y2 displayed-year)
        (year))
    (increment-calendar-month m1 y1 -1)
    (increment-calendar-month m2 y2 1)
    (let* ((start-date (calendar-absolute-from-gregorian
                        (list m1 1 y1)))
           (end-date (calendar-absolute-from-gregorian
                      (list m2 (calendar-last-day-of-month m2 y2) y2)))
           (julian-start (calendar-julian-from-absolute start-date))
           (julian-end (calendar-julian-from-absolute end-date))
           (julian-y1 (extract-calendar-year julian-start))
           (julian-y2 (extract-calendar-year julian-end)))
      (setq year (if (< 10 month) julian-y1 julian-y2))
      (let ((date (calendar-gregorian-from-absolute
                   (calendar-absolute-from-julian
                    (list month day year)))))
        (if (calendar-date-is-visible-p date)
            (list (list date string)))))))

(defun diary-julian-date ()
  "Julian calendar equivalent of date diary entry."
  (format "Julian date: %s" (calendar-julian-date-string date)))

(defun calendar-absolute-from-astro (d)
  "Absolute date of astronomical (Julian) day number D."
  (- d 1721424.5))

(defun calendar-astro-from-absolute (d)
  "Astronomical (Julian) day number of absolute date D."
  (+ d 1721424.5))

(defun calendar-astro-date-string (&optional date)
  "String of astronomical (Julian) day number after noon UTC of Gregorian DATE.
Defaults to today's date if DATE is not given."
  (int-to-string
   (ceiling
    (calendar-astro-from-absolute
     (calendar-absolute-from-gregorian
      (or date (calendar-current-date)))))))

(defun calendar-print-astro-day-number ()
  "Show astronomical (Julian) day number after noon UTC on date shown by cursor."
  (interactive)
  (message
   "Astronomical (Julian) day number (at noon UTC): %s.0"
   (calendar-astro-date-string (calendar-cursor-to-date t))))

(defun calendar-goto-astro-day-number (daynumber &optional noecho)
  "Move cursor to astronomical (Julian) DAYNUMBER.
Echo astronomical (Julian) day number unless NOECHO is t."
  (interactive (list (calendar-read
                      "Astronomical (Julian) day number (>1721425): "
                      '(lambda (x) (> x 1721425)))))
  (calendar-goto-date
   (calendar-gregorian-from-absolute
    (floor
     (calendar-absolute-from-astro daynumber))))
  (or noecho (calendar-print-astro-day-number)))

(defun diary-astro-day-number ()
  "Astronomical (Julian) day number diary entry."
  (format "Astronomical (Julian) day number at noon UTC: %s.0"
          (calendar-astro-date-string date)))

(provide 'cal-julian)

;;; cal-julian.el ends here
Commit	Line	Data
0808d911 ER	1	;;; cal-julian.el --- calendar functions for the Julian calendar.
0808d911 ER	2
a96a5fca	3	;; Copyright (C) 1995, 1997 Free Software Foundation, Inc.
0808d911 ER	4
	5	;; Author: Edward M. Reingold <reingold@cs.uiuc.edu>
	6	;; Keywords: calendar
	7	;; Human-Keywords: Julian calendar, Julian day number, calendar, diary
	8
	9	;; This file is part of GNU Emacs.
	10
	11	;; GNU Emacs is free software; you can redistribute it and/or modify
	12	;; it under the terms of the GNU General Public License as published by
	13	;; the Free Software Foundation; either version 2, or (at your option)
	14	;; any later version.
	15
	16	;; GNU Emacs is distributed in the hope that it will be useful,
	17	;; but WITHOUT ANY WARRANTY; without even the implied warranty of
	18	;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	19	;; GNU General Public License for more details.
	20
	21	;; You should have received a copy of the GNU General Public License
b578f267 EN	22	;; along with GNU Emacs; see the file COPYING. If not, write to the
	23	;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
	24	;; Boston, MA 02111-1307, USA.
0808d911 ER	25
	26	;;; Commentary:
	27
	28	;; This collection of functions implements the features of calendar.el and
	29	;; diary.el that deal with the Julian calendar.
	30
a96a5fca PE	31	;; Technical details of all the calendrical calculations can be found in
	32	;; ``Calendrical Calculations'' by Nachum Dershowitz and Edward M. Reingold,
	33	;; Cambridge University Press (1997).
	34
0808d911 ER	35	;; Comments, corrections, and improvements should be sent to
	36	;; Edward M. Reingold Department of Computer Science
	37	;; (217) 333-6733 University of Illinois at Urbana-Champaign
	38	;; reingold@cs.uiuc.edu 1304 West Springfield Avenue
	39	;; Urbana, Illinois 61801
	40
	41	;;; Code:
	42
	43	(require 'calendar)
	44
	45	(defun calendar-julian-from-absolute (date)
	46	"Compute the Julian (month day year) corresponding to the absolute DATE.
	47	The absolute date is the number of days elapsed since the (imaginary)
	48	Gregorian date Sunday, December 31, 1 BC."
	49	(let* ((approx (/ (+ date 2) 366));; Approximation from below.
	50	(year ;; Search forward from the approximation.
	51	(+ approx
	52	(calendar-sum y approx
	53	(>= date (calendar-absolute-from-julian (list 1 1 (1+ y))))
	54	1)))
	55	(month ;; Search forward from January.
	56	(1+ (calendar-sum m 1
	57	(> date
	58	(calendar-absolute-from-julian
	59	(list m
	60	(if (and (= m 2) (= (% year 4) 0))
	61	29
	62	(aref [31 28 31 30 31 30 31 31 30 31 30 31]
	63	(1- m)))
	64	year)))
	65	1)))
	66	(day ;; Calculate the day by subtraction.
	67	(- date (1- (calendar-absolute-from-julian (list month 1 year))))))
	68	(list month day year)))
	69
	70	(defun calendar-absolute-from-julian (date)
	71	"The number of days elapsed between the Gregorian date 12/31/1 BC and DATE.
	72	The Gregorian date Sunday, December 31, 1 BC is imaginary."
	73	(let ((month (extract-calendar-month date))
	74	(day (extract-calendar-day date))
	75	(year (extract-calendar-year date)))
	76	(+ (calendar-day-number date)
	77	(if (and (= (% year 100) 0)
	78	(/= (% year 400) 0)
	79	(> month 2))
	80	1 0);; Correct for Julian but not Gregorian leap year.
	81	(* 365 (1- year))
	82	(/ (1- year) 4)
	83	-2)))
	84
	85	(defun calendar-julian-date-string (&optional date)
	86	"String of Julian date of Gregorian DATE.
	87	Defaults to today's date if DATE is not given.
	88	Driven by the variable `calendar-date-display-form'."
	89	(calendar-date-string
	90	(calendar-julian-from-absolute
	91	(calendar-absolute-from-gregorian
	92	(or date (calendar-current-date))))
	93	nil t))
	94
	95	(defun calendar-print-julian-date ()
	96	"Show the Julian calendar equivalent of the date under the cursor."
	97	(interactive)
	98	(message "Julian date: %s"
99	(calendar-julian-date-string (calendar-cursor-to-date t))))
100
101	(defun calendar-goto-julian-date (date &optional noecho)
102	"Move cursor to Julian DATE; echo Julian date unless NOECHO is t."
103	(interactive
104	(let* ((today (calendar-current-date))
105	(year (calendar-read
106	"Julian calendar year (>0): "
107	'(lambda (x) (> x 0))
108	(int-to-string
109	(extract-calendar-year
110	(calendar-julian-from-absolute
111	(calendar-absolute-from-gregorian
112	today))))))
113	(month-array calendar-month-name-array)
114	(completion-ignore-case t)
b5394859	115	(month (cdr (assoc-ignore-case
0808d911 ER	116	(completing-read
	117	"Julian calendar month name: "
	118	(mapcar 'list (append month-array nil))
b5394859 RS	119	nil t)
b5394859 RS	120	(calendar-make-alist month-array 1))))
0808d911 ER	121	(last
	122	(if (and (zerop (% year 4)) (= month 2))
	123	29
	124	(aref [31 28 31 30 31 30 31 31 30 31 30 31] (1- month))))
	125	(day (calendar-read
	126	(format "Julian calendar day (%d-%d): "
	127	(if (and (= year 1) (= month 1)) 3 1) last)
	128	'(lambda (x)
	129	(and (< (if (and (= year 1) (= month 1)) 2 0) x)
	130	(<= x last))))))
	131	(list (list month day year))))
	132	(calendar-goto-date (calendar-gregorian-from-absolute
	133	(calendar-absolute-from-julian date)))
	134	(or noecho (calendar-print-julian-date)))
	135
	136	(defun holiday-julian (month day string)
	137	"Holiday on MONTH, DAY (Julian) called STRING.
	138	If MONTH, DAY (Julian) is visible, the value returned is corresponding
	139	Gregorian date in the form of the list (((month day year) STRING)). Returns
	140	nil if it is not visible in the current calendar window."
	141	(let ((m1 displayed-month)
	142	(y1 displayed-year)
	143	(m2 displayed-month)
	144	(y2 displayed-year)
	145	(year))
	146	(increment-calendar-month m1 y1 -1)
	147	(increment-calendar-month m2 y2 1)
	148	(let* ((start-date (calendar-absolute-from-gregorian
	149	(list m1 1 y1)))
	150	(end-date (calendar-absolute-from-gregorian
	151	(list m2 (calendar-last-day-of-month m2 y2) y2)))
	152	(julian-start (calendar-julian-from-absolute start-date))
	153	(julian-end (calendar-julian-from-absolute end-date))
	154	(julian-y1 (extract-calendar-year julian-start))
	155	(julian-y2 (extract-calendar-year julian-end)))
	156	(setq year (if (< 10 month) julian-y1 julian-y2))
	157	(let ((date (calendar-gregorian-from-absolute
	158	(calendar-absolute-from-julian
	159	(list month day year)))))
	160	(if (calendar-date-is-visible-p date)
	161	(list (list date string)))))))
	162
	163	(defun diary-julian-date ()
	164	"Julian calendar equivalent of date diary entry."
	165	(format "Julian date: %s" (calendar-julian-date-string date)))
	166
	167	(defun calendar-absolute-from-astro (d)
4ed43fd3	168	"Absolute date of astronomical (Julian) day number D."
0808d911 ER	169	(- d 1721424.5))
	170
	171	(defun calendar-astro-from-absolute (d)
	172	"Astronomical (Julian) day number of absolute date D."
	173	(+ d 1721424.5))
	174
	175	(defun calendar-astro-date-string (&optional date)
	176	"String of astronomical (Julian) day number after noon UTC of Gregorian DATE.
	177	Defaults to today's date if DATE is not given."
	178	(int-to-string
	179	(ceiling
	180	(calendar-astro-from-absolute
	181	(calendar-absolute-from-gregorian
	182	(or date (calendar-current-date)))))))
	183
	184	(defun calendar-print-astro-day-number ()
	185	"Show astronomical (Julian) day number after noon UTC on date shown by cursor."
	186	(interactive)
	187	(message
e9703897	188	"Astronomical (Julian) day number (at noon UTC): %s.0"
0808d911 ER	189	(calendar-astro-date-string (calendar-cursor-to-date t))))
	190
	191	(defun calendar-goto-astro-day-number (daynumber &optional noecho)
	192	"Move cursor to astronomical (Julian) DAYNUMBER.
	193	Echo astronomical (Julian) day number unless NOECHO is t."
	194	(interactive (list (calendar-read
	195	"Astronomical (Julian) day number (>1721425): "
	196	'(lambda (x) (> x 1721425)))))
	197	(calendar-goto-date
	198	(calendar-gregorian-from-absolute
	199	(floor
	200	(calendar-absolute-from-astro daynumber))))
	201	(or noecho (calendar-print-astro-day-number)))
	202
	203	(defun diary-astro-day-number ()
	204	"Astronomical (Julian) day number diary entry."
75697ad9	205	(format "Astronomical (Julian) day number at noon UTC: %s.0"
0808d911 ER	206	(calendar-astro-date-string date)))
	207
	208	(provide 'cal-julian)
	209
	210	;;; cal-julian.el ends here