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

;;; lunar.el --- calendar functions for phases of the moon

;; Copyright (C) 1992-1993, 1995, 1997, 2001-2014 Free Software
;; Foundation, Inc.

;; Author: Edward M. Reingold <reingold@cs.uiuc.edu>
;; Maintainer: Glenn Morris <rgm@gnu.org>
;; Keywords: calendar
;; Human-Keywords: moon, lunar phases, calendar, diary
;; Package: calendar

;; 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 3 of the License, 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.  If not, see <http://www.gnu.org/licenses/>.

;;; Commentary:

;; See calendar.el.

;; Based on ``Astronomical Formulae for Calculators,'' 3rd ed., by Jean Meeus,
;; Willmann-Bell, Inc., 1985 and ``Astronomical Algorithms'' by Jean Meeus,
;; Willmann-Bell, Inc., 1991.
;;
;; WARNING: The calculations will be accurate only to within a few minutes.

;; The author would be delighted to have an astronomically more sophisticated
;; person rewrite the code for the lunar calculations in this file!

;;; Code:

(require 'calendar)
(require 'solar)
(require 'cal-dst)
;; calendar-astro-to-absolute and v versa are cal-autoloads.
;;;(require 'cal-julian)

(defcustom lunar-phase-names
  '("New Moon" "First Quarter Moon" "Full Moon" "Last Quarter Moon")
  "List of names for the lunar phases."
  :type '(list
          (string :tag "New Moon")
          (string :tag "First Quarter Moon")
          (string :tag "Full Moon")
          (string :tag "Last Quarter Moon"))
  :group 'calendar
  :version "23.2")

(defun lunar-phase (index)
  "Local date and time of lunar phase INDEX.
Integer below INDEX/4 gives the lunation number, counting from Jan 1, 1900;
remainder mod 4 gives the phase: 0 new moon, 1 first quarter, 2 full moon,
3 last quarter.  Returns a list (DATE TIME PHASE)."
  (let* ((phase (mod index 4))
         (index (/ index 4.0))
         (time (/ index 1236.85))
         (date (+ (calendar-absolute-from-gregorian '(1 0.5 1900))
                  0.75933
                  (* 29.53058868 index) ; FIXME 29.530588853?
                  (* 0.0001178 time time)
                  (* -0.000000155 time time time)
                  (* 0.00033
                     (solar-sin-degrees (+ 166.56
                                           (* 132.87 time)
                                           (* -0.009173 time time))))))
         (sun-anomaly (mod
                       (+ 359.2242
                          (* 29.105356 index)
                          (* -0.0000333 time time)
                          (* -0.00000347 time time time))
                       360.0))
         (moon-anomaly (mod
                        (+ 306.0253
                           (* 385.81691806 index)
                           (* 0.0107306 time time)
                           (* 0.00001236 time time time))
                        360.0))
         (moon-lat (mod
                    (+ 21.2964
                       (* 390.67050646 index)
                       (* -0.0016528 time time)
                       (* -0.00000239 time time time))
                    360.0))
         (adjustment
          (if (memq phase '(0 2))
              (+ (* (- 0.1734 (* 0.000393 time))
                    (solar-sin-degrees sun-anomaly))
                 (* 0.0021 (solar-sin-degrees (* 2 sun-anomaly)))
                 (* -0.4068 (solar-sin-degrees moon-anomaly))
                 (* 0.0161 (solar-sin-degrees (* 2 moon-anomaly)))
                 (* -0.0004 (solar-sin-degrees (* 3 moon-anomaly)))
                 (* 0.0104 (solar-sin-degrees (* 2 moon-lat)))
                 (* -0.0051 (solar-sin-degrees (+ sun-anomaly moon-anomaly)))
                 (* -0.0074 (solar-sin-degrees (- sun-anomaly moon-anomaly)))
                 (* 0.0004 (solar-sin-degrees (+ (* 2 moon-lat) sun-anomaly)))
                 (* -0.0004 (solar-sin-degrees (- (* 2 moon-lat) sun-anomaly)))
                 (* -0.0006 (solar-sin-degrees
                             (+ (* 2 moon-lat) moon-anomaly)))
                 (* 0.0010 (solar-sin-degrees (- (* 2 moon-lat) moon-anomaly)))
                 (* 0.0005 (solar-sin-degrees
                            (+ (* 2 moon-anomaly) sun-anomaly))))
            (+ (* (- 0.1721 (* 0.0004 time))
                  (solar-sin-degrees sun-anomaly))
               (* 0.0021 (solar-sin-degrees (* 2 sun-anomaly)))
               (* -0.6280 (solar-sin-degrees moon-anomaly))
               (* 0.0089 (solar-sin-degrees (* 2 moon-anomaly)))
               (* -0.0004 (solar-sin-degrees (* 3 moon-anomaly)))
               (* 0.0079 (solar-sin-degrees (* 2 moon-lat)))
               (* -0.0119 (solar-sin-degrees (+ sun-anomaly moon-anomaly)))
               (* -0.0047 (solar-sin-degrees (- sun-anomaly moon-anomaly)))
               (* 0.0003 (solar-sin-degrees (+ (* 2 moon-lat) sun-anomaly)))
               (* -0.0004 (solar-sin-degrees (- (* 2 moon-lat) sun-anomaly)))
               (* -0.0006 (solar-sin-degrees (+ (* 2 moon-lat) moon-anomaly)))
               (* 0.0021 (solar-sin-degrees (- (* 2 moon-lat) moon-anomaly)))
               (* 0.0003 (solar-sin-degrees
                          (+ (* 2 moon-anomaly) sun-anomaly)))
               (* 0.0004 (solar-sin-degrees
                          (- sun-anomaly (* 2 moon-anomaly))))
               (* -0.0003 (solar-sin-degrees
                           (+ (* 2 sun-anomaly) moon-anomaly))))))
         (adj (+ 0.0028
                 (* -0.0004 (solar-cosine-degrees
                             sun-anomaly))
                 (* 0.0003 (solar-cosine-degrees
                            moon-anomaly))))
         (adjustment (cond ((= phase 1) (+ adjustment adj))
                           ((= phase 2) (- adjustment adj))
                           (t adjustment)))
         (date (+ date adjustment))
         (date (+ date (/ (- calendar-time-zone
                             (solar-ephemeris-correction
                              (calendar-extract-year
                               (calendar-gregorian-from-absolute
                                (truncate date)))))
                          60.0 24.0)))
         (time (* 24 (- date (truncate date))))
         (date (calendar-gregorian-from-absolute (truncate date)))
         (adj (dst-adjust-time date time)))
    (list (car adj) (apply 'solar-time-string (cdr adj)) phase)))

(defconst lunar-cycles-per-year 12.3685 ; 365.25/29.530588853
  "Mean number of lunar cycles per 365.25 day year.")

;; FIXME new-moon index; use in lunar-phase-list implies always below.
(defun lunar-index (date)
  "Return the lunar index for Gregorian date DATE.
This is 4 times the approximate number of new moons since 1 Jan 1900.
The factor of 4 allows (mod INDEX 4) to represent the four quarters."
  (* 4 (truncate
        (* lunar-cycles-per-year
           ;; Years since 1900, as a real.
           (+ (calendar-extract-year date)
              (/ (calendar-day-number date) 366.0)
              -1900)))))

(defun lunar-phase-list (month year)
  "List of lunar phases for three months starting with Gregorian MONTH, YEAR."
  (let* ((index (lunar-index (list month 1 year)))
         (new-moon (lunar-phase index))
         (end-date (let ((end-month month)
                         (end-year year))
                     (calendar-increment-month end-month end-year 3)
                     (list (list end-month 1 end-year))))
         ;; Alternative for start-date:
;;;         (calendar-gregorian-from-absolute
;;;          (1- (calendar-absolute-from-gregorian (list month 1 year))))
         (start-date (progn
                       (calendar-increment-month month year -1)
                       (list (list month
                                   (calendar-last-day-of-month month year)
                                   year))))
         list)
    (while (calendar-date-compare new-moon end-date)
      (if (calendar-date-compare start-date new-moon)
          (setq list (append list (list new-moon))))
      (setq index (1+ index)
            new-moon (lunar-phase index)))
    list))

(defun lunar-phase-name (phase)
  "Name of lunar PHASE.
0 = new moon, 1 = first quarter, 2 = full moon, 3 = last quarter."
  (nth phase lunar-phase-names))

(defvar displayed-month)                ; from calendar-generate
(defvar displayed-year)

;;;###cal-autoload
(defun calendar-lunar-phases (&optional event)
  "Create a buffer with the lunar phases for the current calendar window.
If EVENT is non-nil, it's an event indicating the buffer position to
use instead of point."
  (interactive (list last-nonmenu-event))
  ;; If called from a menu, with the calendar window not selected.
  (with-current-buffer
      (if event (window-buffer (posn-window (event-start event)))
        (current-buffer))
    (message "Computing phases of the moon...")
    (let ((m1 displayed-month)
          (y1 displayed-year)
          (m2 displayed-month)
          (y2 displayed-year))
      (calendar-increment-month m1 y1 -1)
      (calendar-increment-month m2 y2 1)
      (calendar-in-read-only-buffer lunar-phases-buffer
        (calendar-set-mode-line
         (if (= y1 y2)
             (format "Phases of the Moon from %s to %s, %d%%-"
                     (calendar-month-name m1) (calendar-month-name m2) y2)
           (format "Phases of the Moon from %s, %d to %s, %d%%-"
                   (calendar-month-name m1) y1 (calendar-month-name m2) y2)))
        (insert
         (mapconcat
          (lambda (x)
            (format "%s: %s %s" (calendar-date-string (car x))
                    (lunar-phase-name (nth 2 x))
                    (cadr x)))
          (lunar-phase-list m1 y1) "\n")))
      (message "Computing phases of the moon...done"))))

;;;###cal-autoload
(define-obsolete-function-alias 'calendar-phases-of-moon
  'calendar-lunar-phases "23.1")

;;;###autoload
(defun lunar-phases (&optional arg)
  "Display the quarters of the moon for last month, this month, and next month.
If called with an optional prefix argument ARG, prompts for month and year.
This function is suitable for execution in an init file."
  (interactive "P")
  (save-excursion
    (let* ((date (if arg (calendar-read-date t)
                   (calendar-current-date)))
           (displayed-month (calendar-extract-month date))
           (displayed-year (calendar-extract-year date)))
      (calendar-lunar-phases))))

;;;###autoload
(define-obsolete-function-alias 'phases-of-moon 'lunar-phases "23.1")

(defvar date)

;; To be called from diary-list-sexp-entries, where DATE is bound.

;;;###diary-autoload
(defun diary-lunar-phases (&optional mark)
  "Moon phases diary entry.
An optional parameter MARK specifies a face or single-character string to
use when highlighting the day in the calendar."
  (let* ((index (lunar-index date))
         (phase (lunar-phase index)))
    (while (calendar-date-compare phase (list date))
      (setq index (1+ index)
            phase (lunar-phase index)))
    (if (calendar-date-equal (car phase) date)
        (cons mark (concat (lunar-phase-name (nth 2 phase)) " "
                           (cadr phase))))))

;;;###diary-autoload
(define-obsolete-function-alias 'diary-phases-of-moon
  'diary-lunar-phases "23.1")

;; For the Chinese calendar the calculations for the new moon need to be more
;; accurate than those above, so we use more terms in the approximation.
(defun lunar-new-moon-time (k)
  "Astronomical (Julian) day number of K th new moon."
  (let* ((T (/ k 1236.85))
         (T2 (* T T))
         (T3 (* T T T))
         (T4 (* T2 T2))
         (JDE (+ 2451550.09765
                 (* 29.530588853 k)
                 (* 0.0001337 T2)
                 (* -0.000000150 T3)
                 (* 0.00000000073 T4)))
         (E (- 1 (* 0.002516 T) (* 0.0000074 T2)))
         (sun-anomaly (+ 2.5534
                         (* 29.10535669 k)
                         (* -0.0000218 T2)
                         (* -0.00000011 T3)))
         (moon-anomaly (+ 201.5643
                          (* 385.81693528 k)
                          (* 0.0107438 T2)
                          (* 0.00001239 T3)
                          (* -0.000000058 T4)))
         (moon-argument (+ 160.7108
                           (* 390.67050274 k)
                           (* -0.0016341 T2)
                           (* -0.00000227 T3)
                           (* 0.000000011 T4)))
         (omega (+ 124.7746
                   (* -1.56375580 k)
                   (* 0.0020691 T2)
                   (* 0.00000215 T3)))
         (A1  (+ 299.77 (*  0.107408 k) (* -0.009173 T2)))
         (A2  (+ 251.88 (*  0.016321 k)))
         (A3  (+ 251.83 (* 26.641886 k)))
         (A4  (+ 349.42 (* 36.412478 k)))
         (A5  (+  84.66 (* 18.206239 k)))
         (A6  (+ 141.74 (* 53.303771 k)))
         (A7  (+ 207.14 (*  2.453732 k)))
         (A8  (+ 154.84 (*  7.306860 k)))
         (A9  (+  34.52 (* 27.261239 k)))
         (A10 (+ 207.19 (*  0.121824 k)))
         (A11 (+ 291.34 (*  1.844379 k)))
         (A12 (+ 161.72 (* 24.198154 k)))
         (A13 (+ 239.56 (* 25.513099 k)))
         (A14 (+ 331.55 (*  3.592518 k)))
         (correction
          (+ (* -0.40720   (solar-sin-degrees moon-anomaly))
             (*  0.17241 E (solar-sin-degrees sun-anomaly))
             (*  0.01608   (solar-sin-degrees (* 2 moon-anomaly)))
             (*  0.01039   (solar-sin-degrees (* 2 moon-argument)))
             (*  0.00739 E (solar-sin-degrees (- moon-anomaly sun-anomaly)))
             (* -0.00514 E (solar-sin-degrees (+ moon-anomaly sun-anomaly)))
             (*  0.00208 E E (solar-sin-degrees (* 2 sun-anomaly)))
             (* -0.00111   (solar-sin-degrees
                            (- moon-anomaly (* 2 moon-argument))))
             (* -0.00057   (solar-sin-degrees
                            (+ moon-anomaly (* 2 moon-argument))))
             (*  0.00056 E (solar-sin-degrees
                            (+ (* 2 moon-anomaly) sun-anomaly)))
             (* -0.00042   (solar-sin-degrees (* 3 moon-anomaly)))
             (*  0.00042 E (solar-sin-degrees
                            (+ sun-anomaly (* 2 moon-argument))))
             (*  0.00038 E (solar-sin-degrees
                            (- sun-anomaly (* 2 moon-argument))))
             (* -0.00024 E (solar-sin-degrees
                            (- (* 2 moon-anomaly) sun-anomaly)))
             (* -0.00017   (solar-sin-degrees omega))
             (* -0.00007   (solar-sin-degrees
                            (+ moon-anomaly (* 2 sun-anomaly))))
             (*  0.00004   (solar-sin-degrees
                            (- (* 2 moon-anomaly) (* 2 moon-argument))))
             (*  0.00004   (solar-sin-degrees (* 3 sun-anomaly)))
             (*  0.00003   (solar-sin-degrees (+ moon-anomaly sun-anomaly
                                                 (* -2 moon-argument))))
             (*  0.00003   (solar-sin-degrees
                            (+ (* 2 moon-anomaly) (* 2 moon-argument))))
             (* -0.00003   (solar-sin-degrees (+ moon-anomaly sun-anomaly
                                                 (* 2 moon-argument))))
             (*  0.00003   (solar-sin-degrees (- moon-anomaly sun-anomaly
                                                 (* -2 moon-argument))))
             (* -0.00002   (solar-sin-degrees (- moon-anomaly sun-anomaly
                                                 (* 2 moon-argument))))
             (* -0.00002   (solar-sin-degrees
                            (+ (* 3 moon-anomaly) sun-anomaly)))
             (*  0.00002   (solar-sin-degrees (* 4 moon-anomaly)))))
         (additional
          (+ (* 0.000325 (solar-sin-degrees A1))
             (* 0.000165 (solar-sin-degrees A2))
             (* 0.000164 (solar-sin-degrees A3))
             (* 0.000126 (solar-sin-degrees A4))
             (* 0.000110 (solar-sin-degrees A5))
             (* 0.000062 (solar-sin-degrees A6))
             (* 0.000060 (solar-sin-degrees A7))
             (* 0.000056 (solar-sin-degrees A8))
             (* 0.000047 (solar-sin-degrees A9))
             (* 0.000042 (solar-sin-degrees A10))
             (* 0.000040 (solar-sin-degrees A11))
             (* 0.000037 (solar-sin-degrees A12))
             (* 0.000035 (solar-sin-degrees A13))
             (* 0.000023 (solar-sin-degrees A14))))
         (newJDE (+ JDE correction additional)))
    (+ newJDE
       (- (solar-ephemeris-correction
           (calendar-extract-year
            (calendar-gregorian-from-absolute
             (floor (calendar-astro-to-absolute newJDE))))))
       (/ calendar-time-zone 60.0 24.0))))

(defun lunar-new-moon-on-or-after (d)
  "Julian day number of first new moon on or after Julian day number D.
The fractional part is the time of day.

The date and time are local time, including any daylight saving rules,
as governed by the values of `calendar-daylight-savings-starts',
`calendar-daylight-savings-starts-time', `calendar-daylight-savings-ends',
`calendar-daylight-savings-ends-time', `calendar-daylight-time-offset', and
`calendar-time-zone'."
  (let* ((date (calendar-gregorian-from-absolute
                (floor (calendar-astro-to-absolute d))))
         (year (+ (calendar-extract-year date)
                  (/ (calendar-day-number date) 365.25)))
         (k (floor (* (- year 2000.0) lunar-cycles-per-year)))
         (date (lunar-new-moon-time k))
         (a-date (progn
                   (while (< date d)
                     (setq k (1+ k)
                           date (lunar-new-moon-time k)))
                   (calendar-astro-to-absolute date)))
         (time (* 24 (- a-date (truncate a-date))))
         (date (calendar-gregorian-from-absolute (truncate a-date)))
         (adj (dst-adjust-time date time)))
    (calendar-astro-from-absolute
     (+ (calendar-absolute-from-gregorian (car adj))
        (/ (cadr adj) 24.0)))))

(provide 'lunar)

;;; lunar.el ends here
Commit	Line	Data
3afbc435	1	;;; lunar.el --- calendar functions for phases of the moon
7e1dae73	2
ba318903	3	;; Copyright (C) 1992-1993, 1995, 1997, 2001-2014 Free Software
ab422c4d	4	;; Foundation, Inc.
7e1dae73 JB	5
7e1dae73 JB	6	;; Author: Edward M. Reingold <reingold@cs.uiuc.edu>
dbfca9c4	7	;; Maintainer: Glenn Morris <rgm@gnu.org>
e9571d2a ER	8	;; Keywords: calendar
e9571d2a ER	9	;; Human-Keywords: moon, lunar phases, calendar, diary
bd78fa1d	10	;; Package: calendar
7e1dae73 JB	11
	12	;; This file is part of GNU Emacs.
	13
2ed66575	14	;; GNU Emacs is free software: you can redistribute it and/or modify
59243403	15	;; it under the terms of the GNU General Public License as published by
2ed66575 GM	16	;; the Free Software Foundation, either version 3 of the License, or
2ed66575 GM	17	;; (at your option) any later version.
59243403	18
7e1dae73	19	;; GNU Emacs is distributed in the hope that it will be useful,
59243403 RS	20	;; but WITHOUT ANY WARRANTY; without even the implied warranty of
	21	;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	22	;; GNU General Public License for more details.
	23
	24	;; You should have received a copy of the GNU General Public License
2ed66575	25	;; along with GNU Emacs. If not, see <http://www.gnu.org/licenses/>.
7e1dae73 JB	26
	27	;;; Commentary:
	28
4bd7ad5f	29	;; See calendar.el.
7e1dae73 JB	30
7e1dae73 JB	31	;; Based on ``Astronomical Formulae for Calculators,'' 3rd ed., by Jean Meeus,
8a45b040 ER	32	;; Willmann-Bell, Inc., 1985 and ``Astronomical Algorithms'' by Jean Meeus,
8a45b040 ER	33	;; Willmann-Bell, Inc., 1991.
7e1dae73 JB	34	;;
	35	;; WARNING: The calculations will be accurate only to within a few minutes.
	36
	37	;; The author would be delighted to have an astronomically more sophisticated
	38	;; person rewrite the code for the lunar calculations in this file!
	39
7e1dae73 JB	40	;;; Code:
7e1dae73 JB	41
164e17e1	42	(require 'calendar)
7e1dae73	43	(require 'solar)
164e17e1	44	(require 'cal-dst)
5c645a20	45	;; calendar-astro-to-absolute and v versa are cal-autoloads.
164e17e1	46	;;;(require 'cal-julian)
7e1dae73	47
b4deec2e GM	48	(defcustom lunar-phase-names
	49	'("New Moon" "First Quarter Moon" "Full Moon" "Last Quarter Moon")
	50	"List of names for the lunar phases."
	51	:type '(list
	52	(string :tag "New Moon")
	53	(string :tag "First Quarter Moon")
	54	(string :tag "Full Moon")
	55	(string :tag "Last Quarter Moon"))
	56	:group 'calendar
	57	:version "23.2")
	58
7e1dae73 JB	59	(defun lunar-phase (index)
	60	"Local date and time of lunar phase INDEX.
	61	Integer below INDEX/4 gives the lunation number, counting from Jan 1, 1900;
	62	remainder mod 4 gives the phase: 0 new moon, 1 first quarter, 2 full moon,
b4deec2e	63	3 last quarter. Returns a list (DATE TIME PHASE)."
b6c0aabf	64	(let* ((phase (mod index 4))
7e1dae73 JB	65	(index (/ index 4.0))
	66	(time (/ index 1236.85))
	67	(date (+ (calendar-absolute-from-gregorian '(1 0.5 1900))
	68	0.75933
b4deec2e	69	(* 29.53058868 index) ; FIXME 29.530588853?
7e1dae73 JB	70	(* 0.0001178 time time)
	71	(* -0.000000155 time time time)
	72	(* 0.00033
	73	(solar-sin-degrees (+ 166.56
	74	(* 132.87 time)
	75	(* -0.009173 time time))))))
e7bb3aeb	76	(sun-anomaly (mod
7e1dae73 JB	77	(+ 359.2242
	78	(* 29.105356 index)
	79	(* -0.0000333 time time)
	80	(* -0.00000347 time time time))
	81	360.0))
e7bb3aeb	82	(moon-anomaly (mod
7e1dae73 JB	83	(+ 306.0253
	84	(* 385.81691806 index)
	85	(* 0.0107306 time time)
	86	(* 0.00001236 time time time))
	87	360.0))
e7bb3aeb	88	(moon-lat (mod
7e1dae73 JB	89	(+ 21.2964
	90	(* 390.67050646 index)
	91	(* -0.0016528 time time)
	92	(* -0.00000239 time time time))
	93	360.0))
	94	(adjustment
	95	(if (memq phase '(0 2))
	96	(+ (* (- 0.1734 (* 0.000393 time))
	97	(solar-sin-degrees sun-anomaly))
	98	(* 0.0021 (solar-sin-degrees (* 2 sun-anomaly)))
	99	(* -0.4068 (solar-sin-degrees moon-anomaly))
	100	(* 0.0161 (solar-sin-degrees (* 2 moon-anomaly)))
	101	(* -0.0004 (solar-sin-degrees (* 3 moon-anomaly)))
	102	(* 0.0104 (solar-sin-degrees (* 2 moon-lat)))
	103	(* -0.0051 (solar-sin-degrees (+ sun-anomaly moon-anomaly)))
	104	(* -0.0074 (solar-sin-degrees (- sun-anomaly moon-anomaly)))
	105	(* 0.0004 (solar-sin-degrees (+ (* 2 moon-lat) sun-anomaly)))
	106	(* -0.0004 (solar-sin-degrees (- (* 2 moon-lat) sun-anomaly)))
	107	(* -0.0006 (solar-sin-degrees
	108	(+ (* 2 moon-lat) moon-anomaly)))
	109	(* 0.0010 (solar-sin-degrees (- (* 2 moon-lat) moon-anomaly)))
	110	(* 0.0005 (solar-sin-degrees
	111	(+ (* 2 moon-anomaly) sun-anomaly))))
	112	(+ (* (- 0.1721 (* 0.0004 time))
	113	(solar-sin-degrees sun-anomaly))
	114	(* 0.0021 (solar-sin-degrees (* 2 sun-anomaly)))
	115	(* -0.6280 (solar-sin-degrees moon-anomaly))
	116	(* 0.0089 (solar-sin-degrees (* 2 moon-anomaly)))
	117	(* -0.0004 (solar-sin-degrees (* 3 moon-anomaly)))
	118	(* 0.0079 (solar-sin-degrees (* 2 moon-lat)))
	119	(* -0.0119 (solar-sin-degrees (+ sun-anomaly moon-anomaly)))
	120	(* -0.0047 (solar-sin-degrees (- sun-anomaly moon-anomaly)))
	121	(* 0.0003 (solar-sin-degrees (+ (* 2 moon-lat) sun-anomaly)))
	122	(* -0.0004 (solar-sin-degrees (- (* 2 moon-lat) sun-anomaly)))
	123	(* -0.0006 (solar-sin-degrees (+ (* 2 moon-lat) moon-anomaly)))
	124	(* 0.0021 (solar-sin-degrees (- (* 2 moon-lat) moon-anomaly)))
	125	(* 0.0003 (solar-sin-degrees
	126	(+ (* 2 moon-anomaly) sun-anomaly)))
	127	(* 0.0004 (solar-sin-degrees
	128	(- sun-anomaly (* 2 moon-anomaly))))
	129	(* -0.0003 (solar-sin-degrees
9c0b9187	130	(+ (* 2 sun-anomaly) moon-anomaly))))))
7e1dae73 JB	131	(adj (+ 0.0028
	132	(* -0.0004 (solar-cosine-degrees
	133	sun-anomaly))
	134	(* 0.0003 (solar-cosine-degrees
	135	moon-anomaly))))
	136	(adjustment (cond ((= phase 1) (+ adjustment adj))
	137	((= phase 2) (- adjustment adj))
	138	(t adjustment)))
	139	(date (+ date adjustment))
71ea27ee GM	140	(date (+ date (/ (- calendar-time-zone
71ea27ee GM	141	(solar-ephemeris-correction
e803eab7	142	(calendar-extract-year
80e48f9f	143	(calendar-gregorian-from-absolute
238c5cc1	144	(truncate date)))))
71ea27ee	145	60.0 24.0)))
7e1dae73	146	(time (* 24 (- date (truncate date))))
71ea27ee	147	(date (calendar-gregorian-from-absolute (truncate date)))
8a45b040	148	(adj (dst-adjust-time date time)))
e483c805	149	(list (car adj) (apply 'solar-time-string (cdr adj)) phase)))
7e1dae73	150
b4deec2e GM	151	(defconst lunar-cycles-per-year 12.3685 ; 365.25/29.530588853
	152	"Mean number of lunar cycles per 365.25 day year.")
	153
	154	;; FIXME new-moon index; use in lunar-phase-list implies always below.
	155	(defun lunar-index (date)
	156	"Return the lunar index for Gregorian date DATE.
	157	This is 4 times the approximate number of new moons since 1 Jan 1900.
	158	The factor of 4 allows (mod INDEX 4) to represent the four quarters."
	159	(* 4 (truncate
	160	(* lunar-cycles-per-year
	161	;; Years since 1900, as a real.
	162	(+ (calendar-extract-year date)
	163	(/ (calendar-day-number date) 366.0)
	164	-1900)))))
	165
9c0b9187 GM	166	(defun lunar-phase-list (month year)
9c0b9187 GM	167	"List of lunar phases for three months starting with Gregorian MONTH, YEAR."
b4deec2e GM	168	(let* ((index (lunar-index (list month 1 year)))
	169	(new-moon (lunar-phase index))
	170	(end-date (let ((end-month month)
	171	(end-year year))
e803eab7	172	(calendar-increment-month end-month end-year 3)
4bd7ad5f	173	(list (list end-month 1 end-year))))
b4deec2e GM	174	;; Alternative for start-date:
	175	;;; (calendar-gregorian-from-absolute
	176	;;; (1- (calendar-absolute-from-gregorian (list month 1 year))))
4bd7ad5f	177	(start-date (progn
b4deec2e GM	178	(calendar-increment-month month year -1)
	179	(list (list month
	180	(calendar-last-day-of-month month year)
	181	year))))
4bd7ad5f GM	182	list)
	183	(while (calendar-date-compare new-moon end-date)
	184	(if (calendar-date-compare start-date new-moon)
	185	(setq list (append list (list new-moon))))
	186	(setq index (1+ index)
	187	new-moon (lunar-phase index)))
	188	list))
9c0b9187	189
7e1dae73 JB	190	(defun lunar-phase-name (phase)
	191	"Name of lunar PHASE.
	192	0 = new moon, 1 = first quarter, 2 = full moon, 3 = last quarter."
b4deec2e	193	(nth phase lunar-phase-names))
7e1dae73	194
e803eab7	195	(defvar displayed-month) ; from calendar-generate
9c0b9187 GM	196	(defvar displayed-year)
9c0b9187 GM	197
fb97eeac	198	;;;###cal-autoload
dc67263c GM	199	(defun calendar-lunar-phases (&optional event)
	200	"Create a buffer with the lunar phases for the current calendar window.
	201	If EVENT is non-nil, it's an event indicating the buffer position to
	202	use instead of point."
	203	(interactive (list last-nonmenu-event))
	204	;; If called from a menu, with the calendar window not selected.
	205	(with-current-buffer
	206	(if event (window-buffer (posn-window (event-start event)))
	207	(current-buffer))
	208	(message "Computing phases of the moon...")
	209	(let ((m1 displayed-month)
	210	(y1 displayed-year)
	211	(m2 displayed-month)
	212	(y2 displayed-year))
	213	(calendar-increment-month m1 y1 -1)
	214	(calendar-increment-month m2 y2 1)
	215	(calendar-in-read-only-buffer lunar-phases-buffer
	216	(calendar-set-mode-line
	217	(if (= y1 y2)
	218	(format "Phases of the Moon from %s to %s, %d%%-"
	219	(calendar-month-name m1) (calendar-month-name m2) y2)
	220	(format "Phases of the Moon from %s, %d to %s, %d%%-"
	221	(calendar-month-name m1) y1 (calendar-month-name m2) y2)))
	222	(insert
	223	(mapconcat
	224	(lambda (x)
b4deec2e GM	225	(format "%s: %s %s" (calendar-date-string (car x))
	226	(lunar-phase-name (nth 2 x))
	227	(cadr x)))
dc67263c GM	228	(lunar-phase-list m1 y1) "\n")))
dc67263c GM	229	(message "Computing phases of the moon...done"))))
7e1dae73	230
273fcc9b GM	231	;;;###cal-autoload
	232	(define-obsolete-function-alias 'calendar-phases-of-moon
	233	'calendar-lunar-phases "23.1")
	234
7e1dae73	235	;;;###autoload
273fcc9b	236	(defun lunar-phases (&optional arg)
7e1dae73	237	"Display the quarters of the moon for last month, this month, and next month.
f3924c53	238	If called with an optional prefix argument ARG, prompts for month and year.
865fe16f	239	This function is suitable for execution in an init file."
7e1dae73 JB	240	(interactive "P")
7e1dae73 JB	241	(save-excursion
9c0b9187	242	(let* ((date (if arg (calendar-read-date t)
cc4879d2	243	(calendar-current-date)))
e803eab7 GM	244	(displayed-month (calendar-extract-month date))
e803eab7 GM	245	(displayed-year (calendar-extract-year date)))
273fcc9b GM	246	(calendar-lunar-phases))))
	247
	248	;;;###autoload
	249	(define-obsolete-function-alias 'phases-of-moon 'lunar-phases "23.1")
7e1dae73	250
9c0b9187 GM	251	(defvar date)
9c0b9187 GM	252
8c34d83e	253	;; To be called from diary-list-sexp-entries, where DATE is bound.
9c0b9187	254
fb97eeac	255	;;;###diary-autoload
273fcc9b	256	(defun diary-lunar-phases (&optional mark)
9c0b9187	257	"Moon phases diary entry.
a1506d29	258	An optional parameter MARK specifies a face or single-character string to
e0ab9b68	259	use when highlighting the day in the calendar."
b4deec2e	260	(let* ((index (lunar-index date))
7e1dae73 JB	261	(phase (lunar-phase index)))
7e1dae73 JB	262	(while (calendar-date-compare phase (list date))
9c0b9187 GM	263	(setq index (1+ index)
9c0b9187 GM	264	phase (lunar-phase index)))
7e1dae73	265	(if (calendar-date-equal (car phase) date)
9c0b9187 GM	266	(cons mark (concat (lunar-phase-name (nth 2 phase)) " "
9c0b9187 GM	267	(cadr phase))))))
7e1dae73	268
273fcc9b GM	269	;;;###diary-autoload
	270	(define-obsolete-function-alias 'diary-phases-of-moon
	271	'diary-lunar-phases "23.1")
	272
9c0b9187 GM	273	;; For the Chinese calendar the calculations for the new moon need to be more
9c0b9187 GM	274	;; accurate than those above, so we use more terms in the approximation.
8a45b040 ER	275	(defun lunar-new-moon-time (k)
	276	"Astronomical (Julian) day number of K th new moon."
	277	(let* ((T (/ k 1236.85))
71ea27ee GM	278	(T2 (* T T))
	279	(T3 (* T T T))
	280	(T4 (* T2 T2))
	281	(JDE (+ 2451550.09765
	282	(* 29.530588853 k)
	283	(* 0.0001337 T2)
	284	(* -0.000000150 T3)
	285	(* 0.00000000073 T4)))
	286	(E (- 1 (* 0.002516 T) (* 0.0000074 T2)))
	287	(sun-anomaly (+ 2.5534
	288	(* 29.10535669 k)
	289	(* -0.0000218 T2)
	290	(* -0.00000011 T3)))
	291	(moon-anomaly (+ 201.5643
	292	(* 385.81693528 k)
	293	(* 0.0107438 T2)
	294	(* 0.00001239 T3)
	295	(* -0.000000058 T4)))
	296	(moon-argument (+ 160.7108
	297	(* 390.67050274 k)
	298	(* -0.0016341 T2)
	299	(* -0.00000227 T3)
	300	(* 0.000000011 T4)))
	301	(omega (+ 124.7746
	302	(* -1.56375580 k)
	303	(* 0.0020691 T2)
	304	(* 0.00000215 T3)))
	305	(A1 (+ 299.77 (* 0.107408 k) (* -0.009173 T2)))
	306	(A2 (+ 251.88 (* 0.016321 k)))
	307	(A3 (+ 251.83 (* 26.641886 k)))
	308	(A4 (+ 349.42 (* 36.412478 k)))
	309	(A5 (+ 84.66 (* 18.206239 k)))
	310	(A6 (+ 141.74 (* 53.303771 k)))
	311	(A7 (+ 207.14 (* 2.453732 k)))
	312	(A8 (+ 154.84 (* 7.306860 k)))
	313	(A9 (+ 34.52 (* 27.261239 k)))
	314	(A10 (+ 207.19 (* 0.121824 k)))
	315	(A11 (+ 291.34 (* 1.844379 k)))
	316	(A12 (+ 161.72 (* 24.198154 k)))
	317	(A13 (+ 239.56 (* 25.513099 k)))
	318	(A14 (+ 331.55 (* 3.592518 k)))
	319	(correction
9c0b9187 GM	320	(+ (* -0.40720 (solar-sin-degrees moon-anomaly))
	321	(* 0.17241 E (solar-sin-degrees sun-anomaly))
	322	(* 0.01608 (solar-sin-degrees (* 2 moon-anomaly)))
	323	(* 0.01039 (solar-sin-degrees (* 2 moon-argument)))
	324	(* 0.00739 E (solar-sin-degrees (- moon-anomaly sun-anomaly)))
	325	(* -0.00514 E (solar-sin-degrees (+ moon-anomaly sun-anomaly)))
	326	(* 0.00208 E E (solar-sin-degrees (* 2 sun-anomaly)))
	327	(* -0.00111 (solar-sin-degrees
	328	(- moon-anomaly (* 2 moon-argument))))
	329	(* -0.00057 (solar-sin-degrees
	330	(+ moon-anomaly (* 2 moon-argument))))
	331	(* 0.00056 E (solar-sin-degrees
	332	(+ (* 2 moon-anomaly) sun-anomaly)))
	333	(* -0.00042 (solar-sin-degrees (* 3 moon-anomaly)))
	334	(* 0.00042 E (solar-sin-degrees
	335	(+ sun-anomaly (* 2 moon-argument))))
	336	(* 0.00038 E (solar-sin-degrees
	337	(- sun-anomaly (* 2 moon-argument))))
	338	(* -0.00024 E (solar-sin-degrees
	339	(- (* 2 moon-anomaly) sun-anomaly)))
	340	(* -0.00017 (solar-sin-degrees omega))
	341	(* -0.00007 (solar-sin-degrees
	342	(+ moon-anomaly (* 2 sun-anomaly))))
	343	(* 0.00004 (solar-sin-degrees
	344	(- (* 2 moon-anomaly) (* 2 moon-argument))))
	345	(* 0.00004 (solar-sin-degrees (* 3 sun-anomaly)))
	346	(* 0.00003 (solar-sin-degrees (+ moon-anomaly sun-anomaly
	347	(* -2 moon-argument))))
	348	(* 0.00003 (solar-sin-degrees
	349	(+ (* 2 moon-anomaly) (* 2 moon-argument))))
	350	(* -0.00003 (solar-sin-degrees (+ moon-anomaly sun-anomaly
	351	(* 2 moon-argument))))
	352	(* 0.00003 (solar-sin-degrees (- moon-anomaly sun-anomaly
	353	(* -2 moon-argument))))
	354	(* -0.00002 (solar-sin-degrees (- moon-anomaly sun-anomaly
	355	(* 2 moon-argument))))
	356	(* -0.00002 (solar-sin-degrees
	357	(+ (* 3 moon-anomaly) sun-anomaly)))
	358	(* 0.00002 (solar-sin-degrees (* 4 moon-anomaly)))))
71ea27ee	359	(additional
9c0b9187 GM	360	(+ (* 0.000325 (solar-sin-degrees A1))
	361	(* 0.000165 (solar-sin-degrees A2))
	362	(* 0.000164 (solar-sin-degrees A3))
	363	(* 0.000126 (solar-sin-degrees A4))
	364	(* 0.000110 (solar-sin-degrees A5))
	365	(* 0.000062 (solar-sin-degrees A6))
	366	(* 0.000060 (solar-sin-degrees A7))
	367	(* 0.000056 (solar-sin-degrees A8))
	368	(* 0.000047 (solar-sin-degrees A9))
	369	(* 0.000042 (solar-sin-degrees A10))
	370	(* 0.000040 (solar-sin-degrees A11))
	371	(* 0.000037 (solar-sin-degrees A12))
	372	(* 0.000035 (solar-sin-degrees A13))
	373	(* 0.000023 (solar-sin-degrees A14))))
71ea27ee	374	(newJDE (+ JDE correction additional)))
8a45b040 ER	375	(+ newJDE
8a45b040 ER	376	(- (solar-ephemeris-correction
e803eab7	377	(calendar-extract-year
8a45b040	378	(calendar-gregorian-from-absolute
5c645a20	379	(floor (calendar-astro-to-absolute newJDE))))))
8a45b040 ER	380	(/ calendar-time-zone 60.0 24.0))))
	381
	382	(defun lunar-new-moon-on-or-after (d)
f3924c53 GM	383	"Julian day number of first new moon on or after Julian day number D.
f3924c53 GM	384	The fractional part is the time of day.
8a45b040	385
7b96378f	386	The date and time are local time, including any daylight saving rules,
9c0b9187 GM	387	as governed by the values of `calendar-daylight-savings-starts',
	388	`calendar-daylight-savings-starts-time', `calendar-daylight-savings-ends',
	389	`calendar-daylight-savings-ends-time', `calendar-daylight-time-offset', and
	390	`calendar-time-zone'."
8a45b040	391	(let* ((date (calendar-gregorian-from-absolute
5c645a20	392	(floor (calendar-astro-to-absolute d))))
e803eab7	393	(year (+ (calendar-extract-year date)
71ea27ee	394	(/ (calendar-day-number date) 365.25)))
b4deec2e	395	(k (floor (* (- year 2000.0) lunar-cycles-per-year)))
4bd7ad5f GM	396	(date (lunar-new-moon-time k))
	397	(a-date (progn
	398	(while (< date d)
	399	(setq k (1+ k)
	400	date (lunar-new-moon-time k)))
5c645a20	401	(calendar-astro-to-absolute date)))
4bd7ad5f GM	402	(time (* 24 (- a-date (truncate a-date))))
	403	(date (calendar-gregorian-from-absolute (truncate a-date)))
	404	(adj (dst-adjust-time date time)))
	405	(calendar-astro-from-absolute
	406	(+ (calendar-absolute-from-gregorian (car adj))
	407	(/ (cadr adj) 24.0)))))
8a45b040	408
7e1dae73 JB	409	(provide 'lunar)
	410
	411	;;; lunar.el ends here