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

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

;; Copyright (C) 1992, 1993, 1995, 1997, 2001, 2002, 2003, 2004, 2005,
;;   2006, 2007, 2008  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

;; 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, 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., 51 Franklin Street, Fifth Floor,
;; Boston, MA 02110-1301, USA.

;;; Commentary:

;; This collection of functions implements lunar phases for calendar.el and
;; diary.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!

;; Technical details of all the calendrical calculations can be found in
;; ``Calendrical Calculations: The Millennium Edition'' by Edward M. Reingold
;; and Nachum Dershowitz, Cambridge University Press (2001).

;;; Code:

(defvar date)
(defvar displayed-month)
(defvar displayed-year)

(if (fboundp 'atan)
    (require 'lisp-float-type)
  (error "Lunar calculations impossible since floating point is unavailable"))

(require 'solar)

(defun lunar-phase-list (month year)
  "List of lunar phases for three months starting with Gregorian MONTH, YEAR."
  (let ((end-month month)
        (end-year year)
        (start-month month)
        (start-year year))
    (increment-calendar-month end-month end-year 3)
    (increment-calendar-month start-month start-year -1)
    (let* ((end-date (list (list end-month 1 end-year)))
           (start-date (list (list start-month
                                   (calendar-last-day-of-month
                                    start-month start-year)
                                   start-year)))
           (index (* 4
                     (truncate
                      (* 12.3685
                         (+ year
                            ( / (calendar-day-number (list month 1 year))
                                366.0)
                            -1900)))))
           (new-moon (lunar-phase index))
           (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))
        (setq new-moon (lunar-phase index)))
      list)))

(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."
  (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)
                  (* 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
                              (extract-calendar-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)))

(defun lunar-phase-name (phase)
  "Name of lunar PHASE.
0 = new moon, 1 = first quarter, 2 = full moon, 3 = last quarter."
  (cond ((= 0 phase) "New Moon")
        ((= 1 phase) "First Quarter Moon")
        ((= 2 phase) "Full Moon")
        ((= 3 phase) "Last Quarter Moon")))

;;;###cal-autoload
(defun calendar-phases-of-moon ()
  "Create a buffer with the lunar phases for the current calendar window."
  (interactive)
  (message "Computing phases of the moon...")
  (let ((m1 displayed-month)
        (y1 displayed-year)
        (m2 displayed-month)
        (y2 displayed-year))
    (increment-calendar-month m1 y1 -1)
    (increment-calendar-month m2 y2 1)
    (set-buffer (get-buffer-create lunar-phases-buffer))
    (setq buffer-read-only nil)
    (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)))
    (erase-buffer)
    (insert
     (mapconcat
      (lambda (x)
         (let ((date (car x))
               (time (car (cdr x)))
               (phase (car (cdr (cdr x)))))
           (concat (calendar-date-string date)
                   ": "
                   (lunar-phase-name phase)
                   " "
                   time)))
      (lunar-phase-list m1 y1) "\n"))
    (goto-char (point-min))
    (set-buffer-modified-p nil)
    (setq buffer-read-only t)
    (display-buffer lunar-phases-buffer)
    (message "Computing phases of the moon...done")))

;;;###autoload
(defun phases-of-moon (&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 a .emacs file."
  (interactive "P")
  (save-excursion
    (let* ((date (if arg
                     (calendar-read-date t)
                   (calendar-current-date)))
           (displayed-month (extract-calendar-month date))
           (displayed-year (extract-calendar-year date)))
      (calendar-phases-of-moon))))

;;;###diary-autoload
(defun diary-phases-of-moon (&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 (* 4
                   (truncate
                    (* 12.3685
                       (+ (extract-calendar-year date)
                          ( / (calendar-day-number date)
                              366.0)
                          -1900)))))
         (phase (lunar-phase index)))
    (while (calendar-date-compare phase (list date))
      (setq index (1+ index))
      (setq phase (lunar-phase index)))
    (if (calendar-date-equal (car phase) date)
        (cons mark (concat (lunar-phase-name (car (cdr (cdr phase)))) " "
                (car (cdr phase)))))))

;;  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
           (extract-calendar-year
            (calendar-gregorian-from-absolute
             (floor (calendar-absolute-from-astro 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-absolute-from-astro d))))
         (year (+ (extract-calendar-year date)
		  (/ (calendar-day-number date) 365.25)))
	 (k (floor (* (- year 2000.0) 12.3685)))
         (date (lunar-new-moon-time k)))
    (while (< date d)
      (setq k (1+ k))
      (setq date (lunar-new-moon-time k)))
    (let* ((a-date (calendar-absolute-from-astro 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))
          (/ (car (cdr adj)) 24.0))))))

(provide 'lunar)

;; arch-tag: 72f0b8a4-7bcc-4a1b-b67a-ff53c4a1d222
;;; lunar.el ends here
Commit	Line	Data
3afbc435	1	;;; lunar.el --- calendar functions for phases of the moon
7e1dae73	2
a20b3848	3	;; Copyright (C) 1992, 1993, 1995, 1997, 2001, 2002, 2003, 2004, 2005,
8b72699e	4	;; 2006, 2007, 2008 Free Software 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
7e1dae73 JB	10
	11	;; This file is part of GNU Emacs.
	12
59243403 RS	13	;; GNU Emacs is free software; you can redistribute it and/or modify
59243403 RS	14	;; it under the terms of the GNU General Public License as published by
075969b4	15	;; the Free Software Foundation; either version 3, or (at your option)
59243403 RS	16	;; any later version.
59243403 RS	17
7e1dae73	18	;; GNU Emacs is distributed in the hope that it will be useful,
59243403 RS	19	;; but WITHOUT ANY WARRANTY; without even the implied warranty of
	20	;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	21	;; GNU General Public License for more details.
	22
	23	;; You should have received a copy of the GNU General Public License
b578f267	24	;; along with GNU Emacs; see the file COPYING. If not, write to the
3a35cf56 LK	25	;; Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
3a35cf56 LK	26	;; Boston, MA 02110-1301, USA.
7e1dae73 JB	27
	28	;;; Commentary:
	29
	30	;; This collection of functions implements lunar phases for calendar.el and
	31	;; diary.el.
	32
	33	;; Based on ``Astronomical Formulae for Calculators,'' 3rd ed., by Jean Meeus,
8a45b040 ER	34	;; Willmann-Bell, Inc., 1985 and ``Astronomical Algorithms'' by Jean Meeus,
8a45b040 ER	35	;; Willmann-Bell, Inc., 1991.
7e1dae73 JB	36	;;
	37	;; WARNING: The calculations will be accurate only to within a few minutes.
	38
	39	;; The author would be delighted to have an astronomically more sophisticated
	40	;; person rewrite the code for the lunar calculations in this file!
	41
a96a5fca	42	;; Technical details of all the calendrical calculations can be found in
fffaba77 PE	43	;; ``Calendrical Calculations: The Millennium Edition'' by Edward M. Reingold
fffaba77 PE	44	;; and Nachum Dershowitz, Cambridge University Press (2001).
a96a5fca	45
7e1dae73 JB	46	;;; Code:
7e1dae73 JB	47
04ec3414	48	(defvar date)
0b0f8fa4 GM	49	(defvar displayed-month)
	50	(defvar displayed-year)
	51
7e1dae73 JB	52	(if (fboundp 'atan)
7e1dae73 JB	53	(require 'lisp-float-type)
3afbc435	54	(error "Lunar calculations impossible since floating point is unavailable"))
7e1dae73 JB	55
	56	(require 'solar)
	57
	58	(defun lunar-phase-list (month year)
	59	"List of lunar phases for three months starting with Gregorian MONTH, YEAR."
	60	(let ((end-month month)
	61	(end-year year)
	62	(start-month month)
	63	(start-year year))
	64	(increment-calendar-month end-month end-year 3)
	65	(increment-calendar-month start-month start-year -1)
	66	(let* ((end-date (list (list end-month 1 end-year)))
a1506d29	67	(start-date (list (list start-month
7e1dae73 JB	68	(calendar-last-day-of-month
	69	start-month start-year)
	70	start-year)))
	71	(index (* 4
	72	(truncate
	73	(* 12.3685
	74	(+ year
	75	( / (calendar-day-number (list month 1 year))
	76	366.0)
	77	-1900)))))
	78	(new-moon (lunar-phase index))
	79	(list))
	80	(while (calendar-date-compare new-moon end-date)
	81	(if (calendar-date-compare start-date new-moon)
	82	(setq list (append list (list new-moon))))
	83	(setq index (1+ index))
	84	(setq new-moon (lunar-phase index)))
	85	list)))
	86
	87	(defun lunar-phase (index)
	88	"Local date and time of lunar phase INDEX.
	89	Integer below INDEX/4 gives the lunation number, counting from Jan 1, 1900;
	90	remainder mod 4 gives the phase: 0 new moon, 1 first quarter, 2 full moon,
	91	3 last quarter."
b6c0aabf	92	(let* ((phase (mod index 4))
7e1dae73 JB	93	(index (/ index 4.0))
	94	(time (/ index 1236.85))
	95	(date (+ (calendar-absolute-from-gregorian '(1 0.5 1900))
	96	0.75933
	97	(* 29.53058868 index)
	98	(* 0.0001178 time time)
	99	(* -0.000000155 time time time)
	100	(* 0.00033
	101	(solar-sin-degrees (+ 166.56
	102	(* 132.87 time)
	103	(* -0.009173 time time))))))
e7bb3aeb	104	(sun-anomaly (mod
7e1dae73 JB	105	(+ 359.2242
	106	(* 29.105356 index)
	107	(* -0.0000333 time time)
	108	(* -0.00000347 time time time))
	109	360.0))
e7bb3aeb	110	(moon-anomaly (mod
7e1dae73 JB	111	(+ 306.0253
	112	(* 385.81691806 index)
	113	(* 0.0107306 time time)
	114	(* 0.00001236 time time time))
	115	360.0))
e7bb3aeb	116	(moon-lat (mod
7e1dae73 JB	117	(+ 21.2964
	118	(* 390.67050646 index)
	119	(* -0.0016528 time time)
	120	(* -0.00000239 time time time))
	121	360.0))
	122	(adjustment
	123	(if (memq phase '(0 2))
	124	(+ (* (- 0.1734 (* 0.000393 time))
	125	(solar-sin-degrees sun-anomaly))
	126	(* 0.0021 (solar-sin-degrees (* 2 sun-anomaly)))
	127	(* -0.4068 (solar-sin-degrees moon-anomaly))
	128	(* 0.0161 (solar-sin-degrees (* 2 moon-anomaly)))
	129	(* -0.0004 (solar-sin-degrees (* 3 moon-anomaly)))
	130	(* 0.0104 (solar-sin-degrees (* 2 moon-lat)))
	131	(* -0.0051 (solar-sin-degrees (+ sun-anomaly moon-anomaly)))
	132	(* -0.0074 (solar-sin-degrees (- sun-anomaly moon-anomaly)))
	133	(* 0.0004 (solar-sin-degrees (+ (* 2 moon-lat) sun-anomaly)))
	134	(* -0.0004 (solar-sin-degrees (- (* 2 moon-lat) sun-anomaly)))
	135	(* -0.0006 (solar-sin-degrees
	136	(+ (* 2 moon-lat) moon-anomaly)))
	137	(* 0.0010 (solar-sin-degrees (- (* 2 moon-lat) moon-anomaly)))
	138	(* 0.0005 (solar-sin-degrees
	139	(+ (* 2 moon-anomaly) sun-anomaly))))
	140	(+ (* (- 0.1721 (* 0.0004 time))
	141	(solar-sin-degrees sun-anomaly))
	142	(* 0.0021 (solar-sin-degrees (* 2 sun-anomaly)))
	143	(* -0.6280 (solar-sin-degrees moon-anomaly))
	144	(* 0.0089 (solar-sin-degrees (* 2 moon-anomaly)))
	145	(* -0.0004 (solar-sin-degrees (* 3 moon-anomaly)))
	146	(* 0.0079 (solar-sin-degrees (* 2 moon-lat)))
	147	(* -0.0119 (solar-sin-degrees (+ sun-anomaly moon-anomaly)))
	148	(* -0.0047 (solar-sin-degrees (- sun-anomaly moon-anomaly)))
	149	(* 0.0003 (solar-sin-degrees (+ (* 2 moon-lat) sun-anomaly)))
	150	(* -0.0004 (solar-sin-degrees (- (* 2 moon-lat) sun-anomaly)))
	151	(* -0.0006 (solar-sin-degrees (+ (* 2 moon-lat) moon-anomaly)))
	152	(* 0.0021 (solar-sin-degrees (- (* 2 moon-lat) moon-anomaly)))
	153	(* 0.0003 (solar-sin-degrees
	154	(+ (* 2 moon-anomaly) sun-anomaly)))
	155	(* 0.0004 (solar-sin-degrees
	156	(- sun-anomaly (* 2 moon-anomaly))))
	157	(* -0.0003 (solar-sin-degrees
	158	(+ (* 2 sun-anomaly) moon-anomaly))))))
	159	(adj (+ 0.0028
	160	(* -0.0004 (solar-cosine-degrees
	161	sun-anomaly))
	162	(* 0.0003 (solar-cosine-degrees
	163	moon-anomaly))))
	164	(adjustment (cond ((= phase 1) (+ adjustment adj))
	165	((= phase 2) (- adjustment adj))
	166	(t adjustment)))
	167	(date (+ date adjustment))
238c5cc1 PE	168	(date (+ date (/ (- calendar-time-zone
238c5cc1 PE	169	(solar-ephemeris-correction
80e48f9f JB	170	(extract-calendar-year
80e48f9f JB	171	(calendar-gregorian-from-absolute
238c5cc1 PE	172	(truncate date)))))
238c5cc1 PE	173	60.0 24.0)))
7e1dae73	174	(time (* 24 (- date (truncate date))))
e483c805	175	(date (calendar-gregorian-from-absolute (truncate date)))
8a45b040	176	(adj (dst-adjust-time date time)))
e483c805	177	(list (car adj) (apply 'solar-time-string (cdr adj)) phase)))
7e1dae73 JB	178
	179	(defun lunar-phase-name (phase)
	180	"Name of lunar PHASE.
	181	0 = new moon, 1 = first quarter, 2 = full moon, 3 = last quarter."
	182	(cond ((= 0 phase) "New Moon")
	183	((= 1 phase) "First Quarter Moon")
	184	((= 2 phase) "Full Moon")
	185	((= 3 phase) "Last Quarter Moon")))
	186
fb97eeac	187	;;;###cal-autoload
7e1dae73 JB	188	(defun calendar-phases-of-moon ()
	189	"Create a buffer with the lunar phases for the current calendar window."
	190	(interactive)
	191	(message "Computing phases of the moon...")
	192	(let ((m1 displayed-month)
	193	(y1 displayed-year)
	194	(m2 displayed-month)
cc4879d2	195	(y2 displayed-year))
7e1dae73 JB	196	(increment-calendar-month m1 y1 -1)
	197	(increment-calendar-month m2 y2 1)
	198	(set-buffer (get-buffer-create lunar-phases-buffer))
	199	(setq buffer-read-only nil)
	200	(calendar-set-mode-line
1a380827 RS	201	(if (= y1 y2)
	202	(format "Phases of the Moon from %s to %s, %d%%-"
	203	(calendar-month-name m1) (calendar-month-name m2) y2)
	204	(format "Phases of the Moon from %s, %d to %s, %d%%-"
	205	(calendar-month-name m1) y1 (calendar-month-name m2) y2)))
7e1dae73 JB	206	(erase-buffer)
	207	(insert
	208	(mapconcat
b3a6c0ca	209	(lambda (x)
7e1dae73 JB	210	(let ((date (car x))
	211	(time (car (cdr x)))
	212	(phase (car (cdr (cdr x)))))
	213	(concat (calendar-date-string date)
	214	": "
	215	(lunar-phase-name phase)
	216	" "
	217	time)))
	218	(lunar-phase-list m1 y1) "\n"))
	219	(goto-char (point-min))
	220	(set-buffer-modified-p nil)
	221	(setq buffer-read-only t)
	222	(display-buffer lunar-phases-buffer)
	223	(message "Computing phases of the moon...done")))
	224
	225	;;;###autoload
	226	(defun phases-of-moon (&optional arg)
	227	"Display the quarters of the moon for last month, this month, and next month.
f3924c53	228	If called with an optional prefix argument ARG, prompts for month and year.
7e1dae73 JB	229	This function is suitable for execution in a .emacs file."
	230	(interactive "P")
	231	(save-excursion
46124264	232	(let* ((date (if arg
cc4879d2 ER	233	(calendar-read-date t)
	234	(calendar-current-date)))
	235	(displayed-month (extract-calendar-month date))
	236	(displayed-year (extract-calendar-year date)))
7e1dae73 JB	237	(calendar-phases-of-moon))))
7e1dae73 JB	238
fb97eeac	239	;;;###diary-autoload
e0ab9b68 RS	240	(defun diary-phases-of-moon (&optional mark)
e0ab9b68 RS	241	"Moon phases diary entry.
a1506d29	242	An optional parameter MARK specifies a face or single-character string to
e0ab9b68	243	use when highlighting the day in the calendar."
7e1dae73 JB	244	(let* ((index (* 4
	245	(truncate
	246	(* 12.3685
	247	(+ (extract-calendar-year date)
	248	( / (calendar-day-number date)
	249	366.0)
	250	-1900)))))
	251	(phase (lunar-phase index)))
	252	(while (calendar-date-compare phase (list date))
	253	(setq index (1+ index))
	254	(setq phase (lunar-phase index)))
	255	(if (calendar-date-equal (car phase) date)
e0ab9b68 RS	256	(cons mark (concat (lunar-phase-name (car (cdr (cdr phase)))) " "
e0ab9b68 RS	257	(car (cdr phase)))))))
7e1dae73	258
8a45b040 ER	259	;; For the Chinese calendar the calculations for the new moon need to be more
8a45b040 ER	260	;; accurate than those above, so we use more terms in the approximation.
8a45b040 ER	261	(defun lunar-new-moon-time (k)
	262	"Astronomical (Julian) day number of K th new moon."
	263	(let* ((T (/ k 1236.85))
	264	(T2 (* T T))
	265	(T3 (* T T T))
	266	(T4 (* T2 T2))
	267	(JDE (+ 2451550.09765
	268	(* 29.530588853 k)
	269	(* 0.0001337 T2)
	270	(* -0.000000150 T3)
	271	(* 0.00000000073 T4)))
	272	(E (- 1 (* 0.002516 T) (* 0.0000074 T2)))
	273	(sun-anomaly (+ 2.5534
	274	(* 29.10535669 k)
	275	(* -0.0000218 T2)
	276	(* -0.00000011 T3)))
	277	(moon-anomaly (+ 201.5643
	278	(* 385.81693528 k)
	279	(* 0.0107438 T2)
	280	(* 0.00001239 T3)
	281	(* -0.000000058 T4)))
	282	(moon-argument (+ 160.7108
	283	(* 390.67050274 k)
	284	(* -0.0016341 T2)
	285	(* -0.00000227 T3)
	286	(* 0.000000011 T4)))
	287	(omega (+ 124.7746
	288	(* -1.56375580 k)
	289	(* 0.0020691 T2)
	290	(* 0.00000215 T3)))
	291	(A1 (+ 299.77 (* 0.107408 k) (* -0.009173 T2)))
	292	(A2 (+ 251.88 (* 0.016321 k)))
	293	(A3 (+ 251.83 (* 26.641886 k)))
	294	(A4 (+ 349.42 (* 36.412478 k)))
	295	(A5 (+ 84.66 (* 18.206239 k)))
	296	(A6 (+ 141.74 (* 53.303771 k)))
	297	(A7 (+ 207.14 (* 2.453732 k)))
	298	(A8 (+ 154.84 (* 7.306860 k)))
	299	(A9 (+ 34.52 (* 27.261239 k)))
	300	(A10 (+ 207.19 (* 0.121824 k)))
	301	(A11 (+ 291.34 (* 1.844379 k)))
	302	(A12 (+ 161.72 (* 24.198154 k)))
	303	(A13 (+ 239.56 (* 25.513099 k)))
	304	(A14 (+ 331.55 (* 3.592518 k)))
	305	(correction
	306	(+ (* -0.40720 (solar-sin-degrees moon-anomaly))
	307	(* 0.17241 E (solar-sin-degrees sun-anomaly))
	308	(* 0.01608 (solar-sin-degrees (* 2 moon-anomaly)))
	309	(* 0.01039 (solar-sin-degrees (* 2 moon-argument)))
	310	(* 0.00739 E (solar-sin-degrees (- moon-anomaly sun-anomaly)))
	311	(* -0.00514 E (solar-sin-degrees (+ moon-anomaly sun-anomaly)))
	312	(* 0.00208 E E (solar-sin-degrees (* 2 sun-anomaly)))
	313	(* -0.00111 (solar-sin-degrees
	314	(- moon-anomaly (* 2 moon-argument))))
	315	(* -0.00057 (solar-sin-degrees
	316	(+ moon-anomaly (* 2 moon-argument))))
	317	(* 0.00056 E (solar-sin-degrees
	318	(+ (* 2 moon-anomaly) sun-anomaly)))
	319	(* -0.00042 (solar-sin-degrees (* 3 moon-anomaly)))
	320	(* 0.00042 E (solar-sin-degrees
	321	(+ sun-anomaly (* 2 moon-argument))))
	322	(* 0.00038 E (solar-sin-degrees
	323	(- sun-anomaly (* 2 moon-argument))))
	324	(* -0.00024 E (solar-sin-degrees
325	(- (* 2 moon-anomaly) sun-anomaly)))
326	(* -0.00017 (solar-sin-degrees omega))
327	(* -0.00007 (solar-sin-degrees
328	(+ moon-anomaly (* 2 sun-anomaly))))
329	(* 0.00004 (solar-sin-degrees
330	(- (* 2 moon-anomaly) (* 2 moon-argument))))
331	(* 0.00004 (solar-sin-degrees (* 3 sun-anomaly)))
332	(* 0.00003 (solar-sin-degrees (+ moon-anomaly sun-anomaly
333	(* -2 moon-argument))))
334	(* 0.00003 (solar-sin-degrees
335	(+ (* 2 moon-anomaly) (* 2 moon-argument))))
336	(* -0.00003 (solar-sin-degrees (+ moon-anomaly sun-anomaly
337	(* 2 moon-argument))))
338	(* 0.00003 (solar-sin-degrees (- moon-anomaly sun-anomaly
339	(* -2 moon-argument))))
340	(* -0.00002 (solar-sin-degrees (- moon-anomaly sun-anomaly
341	(* 2 moon-argument))))
342	(* -0.00002 (solar-sin-degrees
343	(+ (* 3 moon-anomaly) sun-anomaly)))
344	(* 0.00002 (solar-sin-degrees (* 4 moon-anomaly)))))
345	(additional
346	(+ (* 0.000325 (solar-sin-degrees A1))
347	(* 0.000165 (solar-sin-degrees A2))
348	(* 0.000164 (solar-sin-degrees A3))
349	(* 0.000126 (solar-sin-degrees A4))
350	(* 0.000110 (solar-sin-degrees A5))
351	(* 0.000062 (solar-sin-degrees A6))
352	(* 0.000060 (solar-sin-degrees A7))
353	(* 0.000056 (solar-sin-degrees A8))
354	(* 0.000047 (solar-sin-degrees A9))
355	(* 0.000042 (solar-sin-degrees A10))
356	(* 0.000040 (solar-sin-degrees A11))
357	(* 0.000037 (solar-sin-degrees A12))
358	(* 0.000035 (solar-sin-degrees A13))
359	(* 0.000023 (solar-sin-degrees A14))))
360	(newJDE (+ JDE correction additional)))
361	(+ newJDE
362	(- (solar-ephemeris-correction
363	(extract-calendar-year
364	(calendar-gregorian-from-absolute
365	(floor (calendar-absolute-from-astro newJDE))))))
366	(/ calendar-time-zone 60.0 24.0))))
367
368	(defun lunar-new-moon-on-or-after (d)
f3924c53 GM	369	"Julian day number of first new moon on or after Julian day number D.
f3924c53 GM	370	The fractional part is the time of day.
8a45b040	371
7b96378f	372	The date and time are local time, including any daylight saving rules,
8a45b040 ER	373	as governed by the values of calendar-daylight-savings-starts,
	374	calendar-daylight-savings-starts-time, calendar-daylight-savings-ends,
	375	calendar-daylight-savings-ends-time, calendar-daylight-time-offset, and
	376	calendar-time-zone."
	377	(let* ((date (calendar-gregorian-from-absolute
	378	(floor (calendar-absolute-from-astro d))))
	379	(year (+ (extract-calendar-year date)
	380	(/ (calendar-day-number date) 365.25)))
	381	(k (floor (* (- year 2000.0) 12.3685)))
	382	(date (lunar-new-moon-time k)))
	383	(while (< date d)
	384	(setq k (1+ k))
	385	(setq date (lunar-new-moon-time k)))
	386	(let* ((a-date (calendar-absolute-from-astro date))
	387	(time (* 24 (- a-date (truncate a-date))))
	388	(date (calendar-gregorian-from-absolute (truncate a-date)))
	389	(adj (dst-adjust-time date time)))
	390	(calendar-astro-from-absolute
	391	(+ (calendar-absolute-from-gregorian (car adj))
	392	(/ (car (cdr adj)) 24.0))))))
	393
7e1dae73 JB	394	(provide 'lunar)
7e1dae73 JB	395
b3a6c0ca	396	;; arch-tag: 72f0b8a4-7bcc-4a1b-b67a-ff53c4a1d222
7e1dae73	397	;;; lunar.el ends here