xref: /386bsd/usr/local/lib/emacs/19.25/lisp/holidays.el (revision a2142627)
1;;; holidays.el --- holiday functions for the calendar package
2
3;;; Copyright (C) 1989, 1990, 1992, 1993, 1994 Free Software Foundation, Inc.
4
5;; Author: Edward M. Reingold <reingold@cs.uiuc.edu>
6;; Keywords: holidays, calendar
7
8;; This file is part of GNU Emacs.
9
10;; GNU Emacs is free software; you can redistribute it and/or modify
11;; it under the terms of the GNU General Public License as published by
12;; the Free Software Foundation; either version 2, or (at your option)
13;; any later version.
14
15;; GNU Emacs is distributed in the hope that it will be useful,
16;; but WITHOUT ANY WARRANTY; without even the implied warranty of
17;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
18;; GNU General Public License for more details.
19
20;; You should have received a copy of the GNU General Public License
21;; along with GNU Emacs; see the file COPYING.  If not, write to
22;; the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
23
24;;; Commentary:
25
26;; This collection of functions implements the holiday features as described
27;; in calendar.el.
28
29;; Comments, corrections, and improvements should be sent to
30;;  Edward M. Reingold               Department of Computer Science
31;;  (217) 333-6733                   University of Illinois at Urbana-Champaign
32;;  reingold@cs.uiuc.edu             1304 West Springfield Avenue
33;;                                   Urbana, Illinois 61801
34
35;; Technical details of all the calendrical calculations can be found in
36;; ``Calendrical Calculations'' by Nachum Dershowitz and Edward M. Reingold,
37;; Software--Practice and Experience, Volume 20, Number 9 (September, 1990),
38;; pages 899-928.  ``Calendrical Calculations, Part II: Three Historical
39;; Calendars'' by E. M. Reingold,  N. Dershowitz, and S. M. Clamen,
40;; Software--Practice and Experience, Volume 23, Number 4 (April, 1993),
41;; pages 383-404.
42
43;; Hard copies of these two papers can be obtained by sending email to
44;; reingold@cs.uiuc.edu with the SUBJECT "send-paper-cal" (no quotes) and
45;; the message BODY containing your mailing address (snail).
46
47;;; Code:
48
49(require 'calendar)
50
51(autoload 'solar-equinoxes-solstices "solar"
52  "Date and time of equinoxes and solstices, if visible in the calendar window.
53Requires floating point."
54  t)
55
56(defun holidays (&optional arg)
57  "Display the holidays for last month, this month, and next month.
58If called with an optional prefix argument, prompts for month and year.
59
60This function is suitable for execution in a .emacs file."
61  (interactive "P")
62  (save-excursion
63    (let* ((completion-ignore-case t)
64           (date (calendar-current-date))
65           (displayed-month
66            (if arg
67                (cdr (assoc
68                      (capitalize
69                       (completing-read
70                        "Month name: "
71                        (mapcar 'list (append calendar-month-name-array nil))
72                        nil t))
73                      (calendar-make-alist calendar-month-name-array)))
74              (extract-calendar-month date)))
75           (displayed-year
76            (if arg
77                (calendar-read
78                 "Year (>0): "
79                 '(lambda (x) (> x 0))
80                 (int-to-string
81                  (extract-calendar-year (calendar-current-date))))
82              (extract-calendar-year date))))
83      (list-calendar-holidays))))
84
85(defun check-calendar-holidays (date)
86  "Check the list of holidays for any that occur on DATE.
87The value returned is a list of strings of relevant holiday descriptions.
88The holidays are those in the list calendar-holidays."
89  (let* ((displayed-month (extract-calendar-month date))
90         (displayed-year (extract-calendar-year date))
91         (h (calendar-holiday-list))
92         (holiday-list))
93    (while h
94      (if (calendar-date-equal date (car (car h)))
95          (setq holiday-list (append holiday-list (cdr (car h)))))
96      (setq h (cdr h)))
97    holiday-list))
98
99(defun calendar-cursor-holidays ()
100  "Find holidays for the date specified by the cursor in the calendar window."
101  (interactive)
102  (message "Checking holidays...")
103  (let* ((date (calendar-cursor-to-date t))
104         (date-string (calendar-date-string date))
105         (holiday-list (check-calendar-holidays date))
106         (holiday-string (mapconcat 'identity holiday-list ";  "))
107         (msg (format "%s:  %s" date-string holiday-string)))
108    (if (not holiday-list)
109        (message "No holidays known for %s" date-string)
110      (if (<= (length msg) (frame-width))
111          (message msg)
112        (set-buffer (get-buffer-create holiday-buffer))
113        (setq buffer-read-only nil)
114        (calendar-set-mode-line date-string)
115        (erase-buffer)
116        (insert (mapconcat 'identity holiday-list "\n"))
117        (goto-char (point-min))
118        (set-buffer-modified-p nil)
119        (setq buffer-read-only t)
120        (display-buffer holiday-buffer)
121        (message "Checking holidays...done")))))
122
123(defun mark-calendar-holidays ()
124  "Mark notable days in the calendar window."
125  (interactive)
126  (setq mark-holidays-in-calendar t)
127  (message "Marking holidays...")
128  (let ((holiday-list (calendar-holiday-list)))
129    (while holiday-list
130      (mark-visible-calendar-date
131       (car (car holiday-list)) calendar-holiday-marker)
132      (setq holiday-list (cdr holiday-list))))
133  (message "Marking holidays...done"))
134
135(defun list-calendar-holidays ()
136  "Create a buffer containing the holidays for the current calendar window.
137The holidays are those in the list calendar-notable-days.  Returns t if any
138holidays are found, nil if not."
139  (interactive)
140  (message "Looking up holidays...")
141  (let ((holiday-list (calendar-holiday-list))
142        (m1 displayed-month)
143        (y1 displayed-year)
144        (m2 displayed-month)
145        (y2 displayed-year))
146    (if (not holiday-list)
147        (progn
148          (message "Looking up holidays...none found")
149          nil)
150      (set-buffer (get-buffer-create holiday-buffer))
151      (setq buffer-read-only nil)
152      (increment-calendar-month m1 y1 -1)
153      (increment-calendar-month m2 y2 1)
154      (calendar-set-mode-line
155       (if (= y1 y2)
156           (format "Notable Dates from %s to %s, %d%%-"
157                   (calendar-month-name m1) (calendar-month-name m2) y2)
158         (format "Notable Dates from %s, %d to %s, %d%%-"
159                 (calendar-month-name m1) y1 (calendar-month-name m2) y2)))
160      (erase-buffer)
161      (insert
162       (mapconcat
163        '(lambda (x) (concat (calendar-date-string (car x))
164                             ": " (car (cdr x))))
165        holiday-list "\n"))
166      (goto-char (point-min))
167      (set-buffer-modified-p nil)
168      (setq buffer-read-only t)
169      (display-buffer holiday-buffer)
170      (message "Looking up holidays...done")
171      t)))
172
173(defun calendar-holiday-list ()
174  "Form the list of holidays that occur on dates in the calendar window.
175The holidays are those in the list calendar-holidays."
176  (let ((p calendar-holidays)
177        (holiday-list))
178    (while p
179      (let* ((holidays
180              (if calendar-debug-sexp
181                  (let ((stack-trace-on-error t))
182                    (eval (car p)))
183                (condition-case nil
184                    (eval (car p))
185                  (error (beep)
186                         (message "Bad holiday list item: %s" (car p))
187                         (sleep-for 2))))))
188        (if holidays
189            (setq holiday-list (append holidays holiday-list))))
190      (setq p (cdr p)))
191    (setq holiday-list (sort holiday-list 'calendar-date-compare))))
192
193;; Below are the functions that calculate the dates of holidays; these
194;; are eval'ed in the function calendar-holiday-list.  If you
195;; write other such functions, be sure to imitate the style used below.
196;; Remember that each function must return a list of items of the form
197;; ((month day year) string) of VISIBLE dates in the calendar window.
198
199(defun holiday-fixed (month day string)
200  "Holiday on MONTH, DAY (Gregorian) called STRING.
201If MONTH, DAY is visible, the value returned is the list (((MONTH DAY year)
202STRING)).  Returns nil if it is not visible in the current calendar window."
203  (let ((m displayed-month)
204        (y displayed-year))
205    (increment-calendar-month m y (- 11 month))
206    (if (> m 9)
207      (list (list (list month day y) string)))))
208
209(defun holiday-float (month dayname n string &optional day)
210  "Holiday on MONTH, DAYNAME (Nth occurrence, Gregorian) called STRING.
211If the Nth DAYNAME in MONTH is visible, the value returned is the list
212\(((MONTH DAY year) STRING)).
213
214If N<0, count backward from the end of MONTH.
215
216An optional parameter DAY means the Nth DAYNAME after/before MONTH DAY.
217
218Returns nil if it is not visible in the current calendar window."
219  (let ((m displayed-month)
220        (y displayed-year))
221    (increment-calendar-month m y (- 11 month))
222    (if (> m 9)
223      (list (list (calendar-nth-named-day n dayname month y day) string)))))
224
225(defun holiday-julian (month day string)
226  "Holiday on MONTH, DAY  (Julian) called STRING.
227If MONTH, DAY (Julian) is visible, the value returned is corresponding
228Gregorian date in the form of the list (((month day year) STRING)).  Returns
229nil if it is not visible in the current calendar window."
230  (let ((m1 displayed-month)
231        (y1 displayed-year)
232        (m2 displayed-month)
233        (y2 displayed-year)
234        (year))
235    (increment-calendar-month m1 y1 -1)
236    (increment-calendar-month m2 y2 1)
237    (let* ((start-date (calendar-absolute-from-gregorian
238                        (list m1 1 y1)))
239           (end-date (calendar-absolute-from-gregorian
240                      (list m2 (calendar-last-day-of-month m2 y2) y2)))
241           (julian-start (calendar-julian-from-absolute start-date))
242           (julian-end (calendar-julian-from-absolute end-date))
243           (julian-y1 (extract-calendar-year julian-start))
244           (julian-y2 (extract-calendar-year julian-end)))
245      (setq year (if (< 10 month) julian-y1 julian-y2))
246      (let ((date (calendar-gregorian-from-absolute
247                   (calendar-absolute-from-julian
248                    (list month day year)))))
249        (if (calendar-date-is-visible-p date)
250            (list (list date string)))))))
251
252(defun holiday-islamic (month day string)
253  "Holiday on MONTH, DAY (Islamic) called STRING.
254If MONTH, DAY (Islamic) is visible, the value returned is corresponding
255Gregorian date in the form of the list (((month day year) STRING)).  Returns
256nil if it is not visible in the current calendar window."
257  (let* ((islamic-date (calendar-islamic-from-absolute
258                        (calendar-absolute-from-gregorian
259                         (list displayed-month 15 displayed-year))))
260         (m (extract-calendar-month islamic-date))
261         (y (extract-calendar-year islamic-date))
262        (date))
263    (if (< m 1)
264        nil;;   Islamic calendar doesn't apply.
265      (increment-calendar-month m y (- 10 month))
266      (if (> m 7);;  Islamic date might be visible
267          (let ((date (calendar-gregorian-from-absolute
268                       (calendar-absolute-from-islamic (list month day y)))))
269            (if (calendar-date-is-visible-p date)
270                (list (list date string))))))))
271
272(defun holiday-hebrew (month day string)
273  "Holiday on MONTH, DAY (Hebrew) called STRING.
274If MONTH, DAY (Hebrew) is visible, the value returned is corresponding
275Gregorian date in the form of the list (((month day year) STRING)).  Returns
276nil if it is not visible in the current calendar window."
277  (if (memq displayed-month;;  This test is only to speed things up a bit;
278            (list          ;;  it works fine without the test too.
279             (if (< 11 month) (- month 11) (+ month 1))
280             (if (< 10 month) (- month 10) (+ month 2))
281             (if (<  9 month) (- month  9) (+ month 3))
282             (if (<  8 month) (- month  8) (+ month 4))
283             (if (<  7 month) (- month  7) (+ month 5))))
284      (let ((m1 displayed-month)
285            (y1 displayed-year)
286            (m2 displayed-month)
287            (y2 displayed-year)
288            (year))
289        (increment-calendar-month m1 y1 -1)
290        (increment-calendar-month m2 y2 1)
291        (let* ((start-date (calendar-absolute-from-gregorian
292                            (list m1 1 y1)))
293               (end-date (calendar-absolute-from-gregorian
294                          (list m2 (calendar-last-day-of-month m2 y2) y2)))
295               (hebrew-start (calendar-hebrew-from-absolute start-date))
296               (hebrew-end (calendar-hebrew-from-absolute end-date))
297               (hebrew-y1 (extract-calendar-year hebrew-start))
298               (hebrew-y2 (extract-calendar-year hebrew-end)))
299          (setq year (if (< 6 month) hebrew-y2 hebrew-y1))
300          (let ((date (calendar-gregorian-from-absolute
301                       (calendar-absolute-from-hebrew
302                        (list month day year)))))
303            (if (calendar-date-is-visible-p date)
304                (list (list date string))))))))
305
306(defun holiday-sexp (sexp string)
307  "Sexp holiday for dates in the calendar window.
308SEXP is an expression in variable `year' evaluates to `date'.
309
310STRING is an expression in `date' that evaluates to the holiday description
311of `date'.
312
313If `date' is visible in the calendar window, the holiday STRING is on that
314date.  If date is nil, or if the date is not visible, there is no holiday."
315  (let ((m displayed-month)
316        (y displayed-year))
317    (increment-calendar-month m y -1)
318    (filter-visible-calendar-holidays
319     (append
320      (let* ((year y)
321             (date (eval sexp))
322             (string (if date (eval string))))
323        (list (list date string)))
324      (let* ((year (1+ y))
325             (date (eval sexp))
326             (string (if date (eval string))))
327        (list (list date string)))))))
328
329(defun holiday-advent ()
330  "Date of Advent, if visible in calendar window."
331  (let ((year displayed-year)
332        (month displayed-month))
333    (increment-calendar-month month year -1)
334    (let ((advent (calendar-gregorian-from-absolute
335                   (calendar-dayname-on-or-before 0
336                    (calendar-absolute-from-gregorian
337                     (list 12 3 year))))))
338      (if (calendar-date-is-visible-p advent)
339          (list (list advent "Advent"))))))
340
341(defun holiday-easter-etc ()
342  "List of dates related to Easter, as visible in calendar window."
343 (if (and (> displayed-month 5) (not all-christian-calendar-holidays))
344     nil;; Ash Wednesday, Good Friday, and Easter are not visible.
345   (let* ((century (1+ (/ displayed-year 100)))
346          (shifted-epact        ;; Age of moon for April 5...
347           (% (+ 14 (* 11 (% displayed-year 19));;     ...by Nicaean rule
348                 (-           ;; ...corrected for the Gregorian century rule
349                  (/ (* 3 century) 4))
350                 (/    ;; ...corrected for Metonic cycle inaccuracy.
351                  (+ 5 (* 8 century)) 25)
352                 (* 30 century));;              Keeps value positive.
353              30))
354          (adjusted-epact       ;;  Adjust for 29.5 day month.
355           (if (or (= shifted-epact 0)
356                   (and (= shifted-epact 1) (< 10 (% displayed-year 19))))
357               (1+ shifted-epact)
358             shifted-epact))
359          (paschal-moon       ;; Day after the full moon on or after March 21.
360           (- (calendar-absolute-from-gregorian (list 4 19 displayed-year))
361              adjusted-epact))
362          (abs-easter (calendar-dayname-on-or-before 0 (+ paschal-moon 7)))
363          (mandatory
364           (list
365            (list (calendar-gregorian-from-absolute abs-easter)
366                  "Easter Sunday")
367            (list (calendar-gregorian-from-absolute (- abs-easter 2))
368                  "Good Friday")
369            (list (calendar-gregorian-from-absolute (- abs-easter 46))
370                  "Ash Wednesday")))
371          (optional
372           (list
373            (list (calendar-gregorian-from-absolute (- abs-easter 63))
374                  "Septuagesima Sunday")
375            (list (calendar-gregorian-from-absolute (- abs-easter 56))
376                  "Sexagesima Sunday")
377            (list (calendar-gregorian-from-absolute (- abs-easter 49))
378                  "Shrove Sunday")
379            (list (calendar-gregorian-from-absolute (- abs-easter 48))
380                  "Shrove Monday")
381            (list (calendar-gregorian-from-absolute (- abs-easter 47))
382                  "Shrove Tuesday")
383            (list (calendar-gregorian-from-absolute (- abs-easter 14))
384                  "Passion Sunday")
385            (list (calendar-gregorian-from-absolute (- abs-easter 7))
386                  "Palm Sunday")
387            (list (calendar-gregorian-from-absolute (- abs-easter 3))
388                  "Maundy Thursday")
389            (list (calendar-gregorian-from-absolute (+ abs-easter 35))
390                  "Rogation Sunday")
391            (list (calendar-gregorian-from-absolute (+ abs-easter 39))
392                  "Ascension Day")
393            (list (calendar-gregorian-from-absolute (+ abs-easter 49))
394                  "Pentecost (Whitsunday)")
395            (list (calendar-gregorian-from-absolute (+ abs-easter 50))
396                  "Whitmunday")
397            (list (calendar-gregorian-from-absolute (+ abs-easter 56))
398                  "Trinity Sunday")
399            (list (calendar-gregorian-from-absolute (+ abs-easter 60))
400                  "Corpus Christi")))
401          (output-list
402           (filter-visible-calendar-holidays mandatory)))
403     (if all-christian-calendar-holidays
404         (setq output-list
405               (append
406                (filter-visible-calendar-holidays optional)
407                output-list)))
408     output-list)))
409
410(defun holiday-greek-orthodox-easter ()
411  "Date of Easter according to the rule of the Council of Nicaea."
412  (let ((m displayed-month)
413        (y displayed-year))
414    (increment-calendar-month m y 1)
415    (let* ((julian-year
416            (extract-calendar-year
417             (calendar-julian-from-absolute
418              (calendar-absolute-from-gregorian
419               (list m (calendar-last-day-of-month m y) y)))))
420           (shifted-epact ;; Age of moon for April 5.
421            (% (+ 14
422                  (* 11 (% julian-year 19)))
423               30))
424           (paschal-moon  ;; Day after full moon on or after March 21.
425            (- (calendar-absolute-from-julian (list 4 19 julian-year))
426               shifted-epact))
427           (nicaean-easter;; Sunday following the Paschal moon
428            (calendar-gregorian-from-absolute
429             (calendar-dayname-on-or-before 0 (+ paschal-moon 7)))))
430      (if (calendar-date-is-visible-p nicaean-easter)
431          (list (list nicaean-easter "Pascha (Greek Orthodox Easter)"))))))
432
433(defun holiday-rosh-hashanah-etc ()
434  "List of dates related to Rosh Hashanah, as visible in calendar window."
435  (if (or (< displayed-month 8)
436          (> displayed-month 11))
437      nil;; None of the dates is visible
438    (let* ((abs-r-h (calendar-absolute-from-hebrew
439                      (list 7 1 (+ displayed-year 3761))))
440            (mandatory
441             (list
442              (list (calendar-gregorian-from-absolute abs-r-h)
443                    (format "Rosh HaShanah %d" (+ 3761 displayed-year)))
444              (list (calendar-gregorian-from-absolute (+ abs-r-h 9))
445                    "Yom Kippur")
446              (list (calendar-gregorian-from-absolute (+ abs-r-h 14))
447                    "Sukkot")
448              (list (calendar-gregorian-from-absolute (+ abs-r-h 21))
449                    "Shemini Atzeret")
450              (list (calendar-gregorian-from-absolute (+ abs-r-h 22))
451                    "Simchat Torah")))
452           (optional
453            (list
454             (list (calendar-gregorian-from-absolute
455                    (calendar-dayname-on-or-before 6 (- abs-r-h 4)))
456                   "Selichot (night)")
457             (list (calendar-gregorian-from-absolute (1- abs-r-h))
458                   "Erev Rosh HaShannah")
459             (list (calendar-gregorian-from-absolute (1+ abs-r-h))
460                   "Rosh HaShanah (second day)")
461             (list (calendar-gregorian-from-absolute
462                    (if (= (% abs-r-h 7) 4) (+ abs-r-h 3) (+ abs-r-h 2)))
463                   "Tzom Gedaliah")
464             (list (calendar-gregorian-from-absolute
465                    (calendar-dayname-on-or-before 6 (+ 7 abs-r-h)))
466                   "Shabbat Shuvah")
467             (list (calendar-gregorian-from-absolute (+ abs-r-h 8))
468                   "Erev Yom Kippur")
469             (list (calendar-gregorian-from-absolute (+ abs-r-h 13))
470                   "Erev Sukkot")
471             (list (calendar-gregorian-from-absolute (+ abs-r-h 15))
472                   "Sukkot (second day)")
473             (list (calendar-gregorian-from-absolute (+ abs-r-h 16))
474                   "Hol Hamoed Sukkot (first day)")
475             (list (calendar-gregorian-from-absolute (+ abs-r-h 17))
476                   "Hol Hamoed Sukkot (second day)")
477             (list (calendar-gregorian-from-absolute (+ abs-r-h 18))
478                   "Hol Hamoed Sukkot (third day)")
479             (list (calendar-gregorian-from-absolute (+ abs-r-h 19))
480                   "Hol Hamoed Sukkot (fourth day)")
481             (list (calendar-gregorian-from-absolute (+ abs-r-h 20))
482                   "Hoshannah Rabbah")))
483            (output-list
484             (filter-visible-calendar-holidays mandatory)))
485      (if all-hebrew-calendar-holidays
486          (setq output-list
487                (append
488                 (filter-visible-calendar-holidays optional)
489                 output-list)))
490      output-list)))
491
492(defun holiday-hanukkah ()
493  "List of dates related to Hanukkah, as visible in calendar window."
494    (if (memq displayed-month;;  This test is only to speed things up a bit;
495              '(10 11 12 1 2));; it works fine without the test too.
496        (let ((m displayed-month)
497              (y displayed-year))
498          (increment-calendar-month m y 1)
499          (let* ((h-y (extract-calendar-year
500                         (calendar-hebrew-from-absolute
501                          (calendar-absolute-from-gregorian
502                           (list m (calendar-last-day-of-month m y) y)))))
503                 (abs-h (calendar-absolute-from-hebrew (list 9 25 h-y))))
504            (filter-visible-calendar-holidays
505             (list
506              (list (calendar-gregorian-from-absolute (1- abs-h))
507                    "Erev Hanukkah")
508              (list (calendar-gregorian-from-absolute abs-h)
509                    "Hanukkah (first day)")
510              (list (calendar-gregorian-from-absolute (1+ abs-h))
511                    "Hanukkah (second day)")
512              (list (calendar-gregorian-from-absolute (+ abs-h 2))
513                    "Hanukkah (third day)")
514              (list (calendar-gregorian-from-absolute (+ abs-h 3))
515                    "Hanukkah (fourth day)")
516              (list (calendar-gregorian-from-absolute (+ abs-h 4))
517                    "Hanukkah (fifth day)")
518              (list (calendar-gregorian-from-absolute (+ abs-h 5))
519                    "Hanukkah (sixth day)")
520              (list (calendar-gregorian-from-absolute (+ abs-h 6))
521                    "Hanukkah (seventh day)")
522              (list (calendar-gregorian-from-absolute (+ abs-h 7))
523                    "Hanukkah (eighth day)")))))))
524
525(defun holiday-passover-etc ()
526  "List of dates related to Passover, as visible in calendar window."
527 (if (< 7 displayed-month)
528      nil;; None of the dates is visible
529    (let* ((abs-p (calendar-absolute-from-hebrew
530                      (list 1 15 (+ displayed-year 3760))))
531           (mandatory
532            (list
533             (list (calendar-gregorian-from-absolute abs-p)
534                   "Passover")
535             (list (calendar-gregorian-from-absolute (+ abs-p 50))
536                   "Shavuot")))
537           (optional
538            (list
539             (list (calendar-gregorian-from-absolute
540                    (calendar-dayname-on-or-before 6 (- abs-p 43)))
541                   "Shabbat Shekalim")
542             (list (calendar-gregorian-from-absolute
543                    (calendar-dayname-on-or-before 6 (- abs-p 30)))
544                   "Shabbat Zachor")
545             (list (calendar-gregorian-from-absolute
546                    (if (= (% abs-p 7) 2) (- abs-p 33) (- abs-p 31)))
547                   "Fast of Esther")
548             (list (calendar-gregorian-from-absolute (- abs-p 31))
549                   "Erev Purim")
550             (list (calendar-gregorian-from-absolute (- abs-p 30))
551                   "Purim")
552             (list (calendar-gregorian-from-absolute
553                    (if (zerop (% abs-p 7)) (- abs-p 28) (- abs-p 29)))
554                   "Shushan Purim")
555             (list (calendar-gregorian-from-absolute
556                    (- (calendar-dayname-on-or-before 6 (- abs-p 14)) 7))
557                   "Shabbat Parah")
558             (list (calendar-gregorian-from-absolute
559                    (calendar-dayname-on-or-before 6 (- abs-p 14)))
560                   "Shabbat HaHodesh")
561             (list (calendar-gregorian-from-absolute
562                    (calendar-dayname-on-or-before 6 (1- abs-p)))
563                   "Shabbat HaGadol")
564             (list (calendar-gregorian-from-absolute (1- abs-p))
565                   "Erev Passover")
566             (list (calendar-gregorian-from-absolute (1+ abs-p))
567                   "Passover (second day)")
568             (list (calendar-gregorian-from-absolute (+ abs-p 2))
569                   "Hol Hamoed Passover (first day)")
570             (list (calendar-gregorian-from-absolute (+ abs-p 3))
571                   "Hol Hamoed Passover (second day)")
572             (list (calendar-gregorian-from-absolute (+ abs-p 4))
573                   "Hol Hamoed Passover (third day)")
574             (list (calendar-gregorian-from-absolute (+ abs-p 5))
575                   "Hol Hamoed Passover (fourth day)")
576             (list (calendar-gregorian-from-absolute (+ abs-p 6))
577                   "Passover (seventh day)")
578             (list (calendar-gregorian-from-absolute (+ abs-p 7))
579                   "Passover (eighth day)")
580             (list (calendar-gregorian-from-absolute (+ abs-p 12))
581                   "Yom HaShoah")
582             (list (calendar-gregorian-from-absolute
583                    (if (zerop (% abs-p 7))
584                        (+ abs-p 18)
585                      (if (= (% abs-p 7) 6)
586                          (+ abs-p 19)
587                        (+ abs-p 20))))
588                   "Yom HaAtzma'ut")
589             (list (calendar-gregorian-from-absolute (+ abs-p 33))
590                   "Lag BaOmer")
591             (list (calendar-gregorian-from-absolute (+ abs-p 43))
592                   "Yom Yerushalim")
593             (list (calendar-gregorian-from-absolute (+ abs-p 49))
594                   "Erev Shavuot")
595             (list (calendar-gregorian-from-absolute (+ abs-p 51))
596                   "Shavuot (second day)")))
597           (output-list
598             (filter-visible-calendar-holidays mandatory)))
599      (if all-hebrew-calendar-holidays
600          (setq output-list
601                (append
602                 (filter-visible-calendar-holidays optional)
603                 output-list)))
604      output-list)))
605
606(defun holiday-tisha-b-av-etc ()
607  "List of dates around Tisha B'Av, as visible in calendar window."
608  (if (or (< displayed-month 5)
609          (> displayed-month 9))
610      nil;; None of the dates is visible
611    (let* ((abs-t-a (calendar-absolute-from-hebrew
612                      (list 5 9 (+ displayed-year 3760)))))
613
614      (filter-visible-calendar-holidays
615       (list
616        (list (calendar-gregorian-from-absolute
617               (if (= (% abs-t-a 7) 6) (- abs-t-a 20) (- abs-t-a 21)))
618              "Tzom Tammuz")
619        (list (calendar-gregorian-from-absolute
620               (calendar-dayname-on-or-before 6 abs-t-a))
621              "Shabbat Hazon")
622        (list (calendar-gregorian-from-absolute
623               (if (= (% abs-t-a 7) 6) (1+ abs-t-a) abs-t-a))
624              "Tisha B'Av")
625        (list (calendar-gregorian-from-absolute
626               (calendar-dayname-on-or-before 6 (+ abs-t-a 7)))
627              "Shabbat Nahamu"))))))
628
629(defun filter-visible-calendar-holidays (l)
630  "Return a list of all visible holidays of those on L."
631  (let ((visible)
632        (p l))
633    (while p
634      (and (car (car p))
635           (calendar-date-is-visible-p (car (car p)))
636           (setq visible (append (list (car p)) visible)))
637      (setq p (cdr p)))
638    visible))
639
640(provide 'holidays)
641
642;;; holidays.el ends here
643