lisp/calendar/holidays.el

   1 ;;; holidays.el --- holiday functions for the calendar package
   2
   3 ;; Copyright (C) 1989, 1990, 1992, 1993, 1994, 1997, 2004 Free
   4 ;;   Software Foundation, Inc.
   5
   6 ;; Author: Edward M. Reingold <reingold@cs.uiuc.edu>
   7 ;; Maintainer: Glenn Morris <gmorris@ast.cam.ac.uk>
   8 ;; Keywords: holidays, calendar
   9
  10 ;; This file is part of GNU Emacs.
  11
  12 ;; GNU Emacs is free software; you can redistribute it and/or modify
  13 ;; it under the terms of the GNU General Public License as published by
  14 ;; the Free Software Foundation; either version 2, or (at your option)
  15 ;; any later version.
  16
  17 ;; GNU Emacs is distributed in the hope that it will be useful,
  18 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  19 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20 ;; GNU General Public License for more details.
  21
  22 ;; You should have received a copy of the GNU General Public License
  23 ;; along with GNU Emacs; see the file COPYING.  If not, write to the
  24 ;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  25 ;; Boston, MA 02111-1307, USA.
  26
  27 ;;; Commentary:
  28
  29 ;; This collection of functions implements the holiday features as described
  30 ;; in calendar.el.
  31
  32 ;; Technical details of all the calendrical calculations can be found in
  33 ;; ``Calendrical Calculations'' by Nachum Dershowitz and Edward M. Reingold,
  34 ;; Cambridge University Press (1997).
  35
  36 ;; An earlier version of the technical details appeared in
  37 ;; ``Calendrical Calculations'' by Nachum Dershowitz and Edward M. Reingold,
  38 ;; Software--Practice and Experience, Volume 20, Number 9 (September, 1990),
  39 ;; pages 899-928.  ``Calendrical Calculations, Part II: Three Historical
  40 ;; Calendars'' by E. M. Reingold,  N. Dershowitz, and S. M. Clamen,
  41 ;; Software--Practice and Experience, Volume 23, Number 4 (April, 1993),
  42 ;; pages 383-404.
  43
  44 ;; Hard copies of these two papers can be obtained by sending email to
  45 ;; reingold@cs.uiuc.edu with the SUBJECT "send-paper-cal" (no quotes) and
  46 ;; the message BODY containing your mailing address (snail).
  47
  48 ;; Comments, corrections, and improvements should be sent to
  49 ;;  Edward M. Reingold               Department of Computer Science
  50 ;;  (217) 333-6733                   University of Illinois at Urbana-Champaign
  51 ;;  reingold@cs.uiuc.edu             1304 West Springfield Avenue
  52 ;;                                   Urbana, Illinois 61801
  53
  54 ;;; Code:
  55
  56 (defvar displayed-month)
  57 (defvar displayed-year)
  58
  59 (require 'calendar)
  60
  61 (autoload 'holiday-julian "cal-julian"
  62   "Holiday on MONTH, DAY  (Julian) called STRING."
  63   t)
  64
  65 (autoload 'holiday-hebrew "cal-hebrew"
  66   "Holiday on MONTH, DAY (Hebrew) called STRING."
  67   t)
  68
  69 (autoload 'holiday-rosh-hashanah-etc "cal-hebrew"
  70   "List of dates related to Rosh Hashanah, as visible in calendar window."
  71   t)
  72
  73 (autoload 'holiday-hanukkah "cal-hebrew"
  74   "List of dates related to Hanukkah, as visible in calendar window."
  75   t)
  76
  77 (autoload 'holiday-passover-etc "cal-hebrew"
  78   "List of dates related to Passover, as visible in calendar window."
  79   t)
  80
  81 (autoload 'holiday-tisha-b-av-etc "cal-hebrew"
  82   "List of dates around Tisha B'Av, as visible in calendar window."
  83   t)
  84
  85 (autoload 'holiday-islamic "cal-islam"
  86   "Holiday on MONTH, DAY (Islamic) called STRING."
  87   t)
  88
  89 (autoload 'holiday-bahai "cal-bahai"
  90   "Holiday on MONTH, DAY (Baha'i) called STRING."
  91   t)
  92
  93 (autoload 'holiday-chinese-new-year "cal-china"
  94   "Date of Chinese New Year."
  95   t)
  96
  97 (autoload 'solar-equinoxes-solstices "solar"
  98   "Date and time of equinoxes and solstices, if visible in the calendar window.
  99 Requires floating point."
 100   t)
 101
 102 ;;;###autoload
 103 (defun holidays (&optional arg)
 104   "Display the holidays for last month, this month, and next month.
 105 If called with an optional prefix argument, prompts for month and year.
 106
 107 This function is suitable for execution in a .emacs file."
 108   (interactive "P")
 109   (save-excursion
 110     (let* ((completion-ignore-case t)
 111            (date (if arg
 112                      (calendar-read-date t)
 113                    (calendar-current-date)))
 114            (displayed-month (extract-calendar-month date))
 115            (displayed-year (extract-calendar-year date)))
 116       (list-calendar-holidays))))
 117
 118 ;;;###autoload
 119 (defun list-holidays (y1 y2 &optional l label)
 120   "Display holidays for years Y1 to Y2 (inclusive).
 121
 122 The optional list of holidays L defaults to `calendar-holidays'.  See the
 123 documentation for that variable for a description of holiday lists.
 124
 125 The optional LABEL is used to label the buffer created."
 126   (interactive
 127    (let* ((start-year (calendar-read
 128                        "Starting year of holidays (>0): "
 129                        '(lambda (x) (> x 0))
 130                        (int-to-string (extract-calendar-year
 131                                        (calendar-current-date)))))
 132           (end-year (calendar-read
 133                        (format "Ending year (inclusive) of holidays (>=%s): "
 134                                start-year)
 135                        '(lambda (x) (>= x start-year))
 136                        (int-to-string start-year)))
 137           (completion-ignore-case t)
 138           (lists
 139            (list
 140             (cons "All" calendar-holidays)
 141             (if (fboundp 'atan)
 142                 (cons "Equinoxes/Solstices"
 143                       (list (list 'solar-equinoxes-solstices))))
 144             (if general-holidays (cons "General" general-holidays))
 145             (if local-holidays (cons "Local" local-holidays))
 146             (if other-holidays (cons "Other" other-holidays))
 147             (if christian-holidays (cons "Christian" christian-holidays))
 148             (if hebrew-holidays (cons "Hebrew" hebrew-holidays))
 149             (if islamic-holidays (cons "Islamic" islamic-holidays))
 150             (if bahai-holidays (cons "Baha'i" bahai-holidays))
 151             (if oriental-holidays (cons "Oriental" oriental-holidays))
 152             (if solar-holidays (cons "Solar" solar-holidays))
 153             (cons "Ask" nil)))
 154           (choice (capitalize
 155                    (completing-read "List (TAB for choices): " lists nil t)))
 156           (which (if (string-equal choice "Ask")
 157                      (eval (read-variable "Enter list name: "))
 158                    (cdr (assoc choice lists))))
 159           (name (if (string-equal choice "Equinoxes/Solstices")
 160                     choice
 161                   (if (member choice '("Ask" ""))
 162                       "Holidays"
 163                     (format "%s Holidays" choice)))))
 164      (list start-year end-year which name)))
 165   (message "Computing holidays...")
 166   (let* ((holiday-buffer "*Holidays*")
 167          (calendar-holidays (if l l calendar-holidays))
 168          (title (or label "Holidays"))
 169          (holiday-list nil)
 170          (s (calendar-absolute-from-gregorian (list 2 1 y1)))
 171          (e (calendar-absolute-from-gregorian (list 11 1 y2)))
 172          (d s)
 173          (never t)
 174          (displayed-month 2)
 175          (displayed-year y1))
 176     (while (or never (<= d e))
 177       (setq holiday-list (append holiday-list (calendar-holiday-list)))
 178       (setq never nil)
 179       (increment-calendar-month displayed-month displayed-year 3)
 180       (setq d (calendar-absolute-from-gregorian
 181                (list displayed-month 1 displayed-year))))
 182     (save-excursion
 183       (set-buffer (get-buffer-create holiday-buffer))
 184       (setq buffer-read-only nil)
 185       (calendar-set-mode-line
 186        (if (= y1 y2)
 187            (format "%s for %s" title y1)
 188          (format "%s for %s-%s" title y1 y2)))
 189       (erase-buffer)
 190       (goto-char (point-min))
 191       (insert
 192        (mapconcat
 193         '(lambda (x) (concat (calendar-date-string (car x))
 194                              ": " (car (cdr x))))
 195         holiday-list "\n"))
 196       (goto-char (point-min))
 197       (set-buffer-modified-p nil)
 198       (setq buffer-read-only t)
 199       (display-buffer holiday-buffer)
 200       (message "Computing holidays...done"))))
 201
 202
 203 (defun check-calendar-holidays (date)
 204   "Check the list of holidays for any that occur on DATE.
 205 The value returned is a list of strings of relevant holiday descriptions.
 206 The holidays are those in the list calendar-holidays."
 207   (let* ((displayed-month (extract-calendar-month date))
 208          (displayed-year (extract-calendar-year date))
 209          (h (calendar-holiday-list))
 210          (holiday-list))
 211     (while h
 212       (if (calendar-date-equal date (car (car h)))
 213           (setq holiday-list (append holiday-list (cdr (car h)))))
 214       (setq h (cdr h)))
 215     holiday-list))
 216
 217 (defun calendar-cursor-holidays ()
 218   "Find holidays for the date specified by the cursor in the calendar window."
 219   (interactive)
 220   (message "Checking holidays...")
 221   (let* ((date (calendar-cursor-to-date t))
 222          (date-string (calendar-date-string date))
 223          (holiday-list (check-calendar-holidays date))
 224          (holiday-string (mapconcat 'identity holiday-list ";  "))
 225          (msg (format "%s:  %s" date-string holiday-string)))
 226     (if (not holiday-list)
 227         (message "No holidays known for %s" date-string)
 228       (if (<= (length msg) (frame-width))
 229           (message "%s" msg)
 230         (set-buffer (get-buffer-create holiday-buffer))
 231         (setq buffer-read-only nil)
 232         (calendar-set-mode-line date-string)
 233         (erase-buffer)
 234         (insert (mapconcat 'identity holiday-list "\n"))
 235         (goto-char (point-min))
 236         (set-buffer-modified-p nil)
 237         (setq buffer-read-only t)
 238         (display-buffer holiday-buffer)
 239         (message "Checking holidays...done")))))
 240
 241 (defun mark-calendar-holidays ()
 242   "Mark notable days in the calendar window."
 243   (interactive)
 244   (setq mark-holidays-in-calendar t)
 245   (message "Marking holidays...")
 246   (let ((holiday-list (calendar-holiday-list)))
 247     (while holiday-list
 248       (mark-visible-calendar-date
 249        (car (car holiday-list)) calendar-holiday-marker)
 250       (setq holiday-list (cdr holiday-list))))
 251   (message "Marking holidays...done"))
 252
 253 (defun list-calendar-holidays ()
 254   "Create a buffer containing the holidays for the current calendar window.
 255 The holidays are those in the list calendar-notable-days.  Returns t if any
 256 holidays are found, nil if not."
 257   (interactive)
 258   (message "Looking up holidays...")
 259   (let ((holiday-list (calendar-holiday-list))
 260         (m1 displayed-month)
 261         (y1 displayed-year)
 262         (m2 displayed-month)
 263         (y2 displayed-year))
 264     (if (not holiday-list)
 265         (progn
 266           (message "Looking up holidays...none found")
 267           nil)
 268       (set-buffer (get-buffer-create holiday-buffer))
 269       (setq buffer-read-only nil)
 270       (increment-calendar-month m1 y1 -1)
 271       (increment-calendar-month m2 y2 1)
 272       (calendar-set-mode-line
 273        (if (= y1 y2)
 274            (format "Notable Dates from %s to %s, %d%%-"
 275                    (calendar-month-name m1) (calendar-month-name m2) y2)
 276          (format "Notable Dates from %s, %d to %s, %d%%-"
 277                  (calendar-month-name m1) y1 (calendar-month-name m2) y2)))
 278       (erase-buffer)
 279       (insert
 280        (mapconcat
 281         '(lambda (x) (concat (calendar-date-string (car x))
 282                              ": " (car (cdr x))))
 283         holiday-list "\n"))
 284       (goto-char (point-min))
 285       (set-buffer-modified-p nil)
 286       (setq buffer-read-only t)
 287       (display-buffer holiday-buffer)
 288       (message "Looking up holidays...done")
 289       t)))
 290
 291 (defun calendar-holiday-list ()
 292   "Form the list of holidays that occur on dates in the calendar window.
 293 The holidays are those in the list calendar-holidays."
 294   (let ((p calendar-holidays)
 295         (holiday-list))
 296     (while p
 297       (let* ((holidays
 298               (if calendar-debug-sexp
 299                   (let ((stack-trace-on-error t))
 300                     (eval (car p)))
 301                 (condition-case nil
 302                     (eval (car p))
 303                   (error (beep)
 304                          (message "Bad holiday list item: %s" (car p))
 305                          (sleep-for 2))))))
 306         (if holidays
 307             (setq holiday-list (append holidays holiday-list))))
 308       (setq p (cdr p)))
 309     (setq holiday-list (sort holiday-list 'calendar-date-compare))))
 310
 311 ;; Below are the functions that calculate the dates of holidays; these
 312 ;; are eval'ed in the function calendar-holiday-list.  If you
 313 ;; write other such functions, be sure to imitate the style used below.
 314 ;; Remember that each function must return a list of items of the form
 315 ;; ((month day year) string) of VISIBLE dates in the calendar window.
 316
 317 (defun holiday-fixed (month day string)
 318   "Holiday on MONTH, DAY (Gregorian) called STRING.
 319 If MONTH, DAY is visible, the value returned is the list (((MONTH DAY year)
 320 STRING)).  Returns nil if it is not visible in the current calendar window."
 321   (let ((m displayed-month)
 322         (y displayed-year))
 323     (increment-calendar-month m y (- 11 month))
 324     (if (> m 9)
 325       (list (list (list month day y) string)))))
 326
 327 (defun holiday-float (month dayname n string &optional day)
 328   "Holiday on MONTH, DAYNAME (Nth occurrence) called STRING.
 329 If the Nth DAYNAME in MONTH is visible, the value returned is the list
 330 \(((MONTH DAY year) STRING)).
 331
 332 If N<0, count backward from the end of MONTH.
 333
 334 An optional parameter DAY means the Nth DAYNAME on or after/before MONTH DAY.
 335
 336 Returns nil if it is not visible in the current calendar window."
 337 ;; This is messy because the holiday may be visible, while the date on which
 338 ;; it is based is not.  For example, the first Monday after December 30 may be
 339 ;; visible when January is not.  For large values of |n| the problem is more
 340 ;; grotesque.  If we didn't have to worry about such cases, we could just use
 341
 342 ;;  (let ((m displayed-month)
 343 ;;        (y displayed-year))
 344 ;;    (increment-calendar-month m y (- 11 month))
 345 ;;    (if (> m 9); month in year y is visible
 346 ;;      (list (list (calendar-nth-named-day n dayname month y day) string)))))
 347
 348 ;; which is the way the function was originally written.
 349
 350   (let* ((m1 displayed-month)
 351          (y1 displayed-year)
 352          (m2 m1)
 353          (y2 y1))
 354     (increment-calendar-month m1 y1 -1)
 355     (increment-calendar-month m2 y2 1)
 356     (let* ((d1;  first possible base date for holiday
 357             (+ (calendar-nth-named-absday 1 dayname m1 y1)
 358                (* -7 n)
 359                (if (> n 0) 1 -7)))
 360            (d2;  last possible base date for holiday
 361             (+ (calendar-nth-named-absday -1 dayname m2 y2)
 362                (* -7 n)
 363                (if (> n 0) 7 -1)))
 364            (y1 (extract-calendar-year (calendar-gregorian-from-absolute d1)))
 365            (y2 (extract-calendar-year (calendar-gregorian-from-absolute d2)))
 366            (y; year of base date
 367             (if (or (= y1 y2) (> month 9))
 368                   y1
 369                 y2))
 370            (d; day of base date
 371             (or day (if (> n 0)
 372                         1
 373                       (calendar-last-day-of-month month y))))
 374            (date; base date for holiday
 375             (calendar-absolute-from-gregorian (list month d y))))
 376       (if (and (<= d1 date) (<= date d2))
 377           (list (list (calendar-nth-named-day n dayname month y d)
 378                       string))))))
 379
 380 (defun holiday-sexp (sexp string)
 381   "Sexp holiday for dates in the calendar window.
 382 SEXP is an expression in variable `year' evaluates to `date'.
 383
 384 STRING is an expression in `date' that evaluates to the holiday description
 385 of `date'.
 386
 387 If `date' is visible in the calendar window, the holiday STRING is on that
 388 date.  If date is nil, or if the date is not visible, there is no holiday."
 389   (let ((m displayed-month)
 390         (y displayed-year))
 391     (increment-calendar-month m y -1)
 392     (filter-visible-calendar-holidays
 393      (append
 394       (let* ((year y)
 395              (date (eval sexp))
 396              (string (if date (eval string))))
 397         (list (list date string)))
 398       (let* ((year (1+ y))
 399              (date (eval sexp))
 400              (string (if date (eval string))))
 401         (list (list date string)))))))
 402
 403 (defun holiday-advent (n string)
 404   "Date of Nth day after advent (named STRING), if visible in calendar window."
 405   (let ((year displayed-year)
 406         (month displayed-month))
 407     (increment-calendar-month month year -1)
 408     (let ((advent (calendar-gregorian-from-absolute
 409                    (+ n
 410                       (calendar-dayname-on-or-before
 411                        0
 412                        (calendar-absolute-from-gregorian
 413                         (list 12 3 year)))))))
 414       (if (calendar-date-is-visible-p advent)
 415           (list (list advent string))))))
 416
 417 (defun holiday-easter-etc (n string)
 418   "Date of Nth day after Easter (named STRING), if visible in calendar window."
 419   (let* ((century (1+ (/ displayed-year 100)))
 420          (shifted-epact        ;; Age of moon for April 5...
 421           (% (+ 14 (* 11 (% displayed-year 19));;     ...by Nicaean rule
 422                 (-           ;; ...corrected for the Gregorian century rule
 423                  (/ (* 3 century) 4))
 424                 (/    ;; ...corrected for Metonic cycle inaccuracy.
 425                  (+ 5 (* 8 century)) 25)
 426                 (* 30 century));;              Keeps value positive.
 427              30))
 428          (adjusted-epact       ;;  Adjust for 29.5 day month.
 429           (if (or (= shifted-epact 0)
 430                   (and (= shifted-epact 1) (< 10 (% displayed-year 19))))
 431               (1+ shifted-epact)
 432             shifted-epact))
 433          (paschal-moon       ;; Day after the full moon on or after March 21.
 434           (- (calendar-absolute-from-gregorian (list 4 19 displayed-year))
 435              adjusted-epact))
 436          (abs-easter (calendar-dayname-on-or-before 0 (+ paschal-moon 7)))
 437          (mandatory
 438            (list
 439             (list (calendar-gregorian-from-absolute (+ abs-easter n))
 440                   string)))
 441          (output-list (filter-visible-calendar-holidays mandatory)))
 442     output-list))
 443
 444 (defun holiday-greek-orthodox-easter ()
 445   "Date of Easter according to the rule of the Council of Nicaea."
 446   (let ((m displayed-month)
 447         (y displayed-year))
 448     (increment-calendar-month m y 1)
 449     (let* ((julian-year
 450             (extract-calendar-year
 451              (calendar-julian-from-absolute
 452               (calendar-absolute-from-gregorian
 453                (list m (calendar-last-day-of-month m y) y)))))
 454            (shifted-epact ;; Age of moon for April 5.
 455             (% (+ 14
 456                   (* 11 (% julian-year 19)))
 457                30))
 458            (paschal-moon  ;; Day after full moon on or after March 21.
 459             (- (calendar-absolute-from-julian (list 4 19 julian-year))
 460                shifted-epact))
 461            (nicaean-easter;; Sunday following the Paschal moon
 462             (calendar-gregorian-from-absolute
 463              (calendar-dayname-on-or-before 0 (+ paschal-moon 7)))))
 464       (if (calendar-date-is-visible-p nicaean-easter)
 465           (list (list nicaean-easter "Pascha (Greek Orthodox Easter)"))))))
 466
 467 (defun filter-visible-calendar-holidays (l)
 468   "Return a list of all visible holidays of those on L."
 469   (let ((visible)
 470         (p l))
 471     (while p
 472       (and (car (car p))
 473            (calendar-date-is-visible-p (car (car p)))
 474            (setq visible (append (list (car p)) visible)))
 475       (setq p (cdr p)))
 476     visible))
 477
 478 (provide 'holidays)
 479
 480 ;;; arch-tag: 48eb3117-75a7-4dbe-8fd9-873c3cbb0d37
 481 ;;; holidays.el ends here