lisp/calendar/holidays.el

   1 ;;; holidays.el --- holiday functions for the calendar package
   2
   3 ;; Copyright (C) 1989, 90, 92, 93, 94, 1997 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 the
  22 ;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  23 ;; Boston, MA 02111-1307, USA.
  24
  25 ;;; Commentary:
  26
  27 ;; This collection of functions implements the holiday features as described
  28 ;; in calendar.el.
  29
  30 ;; Technical details of all the calendrical calculations can be found in
  31 ;; ``Calendrical Calculations'' by Nachum Dershowitz and Edward M. Reingold,
  32 ;; Cambridge University Press (1997).
  33
  34 ;; An earlier version of the technical details appeared in
  35 ;; ``Calendrical Calculations'' by Nachum Dershowitz and Edward M. Reingold,
  36 ;; Software--Practice and Experience, Volume 20, Number 9 (September, 1990),
  37 ;; pages 899-928.  ``Calendrical Calculations, Part II: Three Historical
  38 ;; Calendars'' by E. M. Reingold,  N. Dershowitz, and S. M. Clamen,
  39 ;; Software--Practice and Experience, Volume 23, Number 4 (April, 1993),
  40 ;; pages 383-404.
  41
  42 ;; Hard copies of these two papers can be obtained by sending email to
  43 ;; reingold@cs.uiuc.edu with the SUBJECT "send-paper-cal" (no quotes) and
  44 ;; the message BODY containing your mailing address (snail).
  45
  46 ;; Comments, corrections, and improvements should be sent to
  47 ;;  Edward M. Reingold               Department of Computer Science
  48 ;;  (217) 333-6733                   University of Illinois at Urbana-Champaign
  49 ;;  reingold@cs.uiuc.edu             1304 West Springfield Avenue
  50 ;;                                   Urbana, Illinois 61801
  51
  52 ;;; Code:
  53
  54 (defvar displayed-month)
  55 (defvar displayed-year)
  56
  57 (require 'calendar)
  58
  59 (autoload 'holiday-julian "cal-julian"
  60   "Holiday on MONTH, DAY  (Julian) called STRING."
  61   t)
  62
  63 (autoload 'holiday-hebrew "cal-hebrew"
  64   "Holiday on MONTH, DAY (Hebrew) called STRING."
  65   t)
  66
  67 (autoload 'holiday-rosh-hashanah-etc "cal-hebrew"
  68   "List of dates related to Rosh Hashanah, as visible in calendar window."
  69   t)
  70
  71 (autoload 'holiday-hanukkah "cal-hebrew"
  72   "List of dates related to Hanukkah, as visible in calendar window."
  73   t)
  74
  75 (autoload 'holiday-passover-etc "cal-hebrew"
  76   "List of dates related to Passover, as visible in calendar window."
  77   t)
  78
  79 (autoload 'holiday-tisha-b-av-etc "cal-hebrew"
  80   "List of dates around Tisha B'Av, as visible in calendar window."
  81   t)
  82
  83 (autoload 'holiday-islamic "cal-islam"
  84   "Holiday on MONTH, DAY (Islamic) called STRING."
  85   t)
  86
  87 (autoload 'holiday-chinese-new-year "cal-china"
  88   "Date of Chinese New Year."
  89   t)
  90
  91 (autoload 'solar-equinoxes-solstices "solar"
  92   "Date and time of equinoxes and solstices, if visible in the calendar window.
  93 Requires floating point."
  94   t)
  95
  96 ;;;###autoload
  97 (defun holidays (&optional arg)
  98   "Display the holidays for last month, this month, and next month.
  99 If called with an optional prefix argument, prompts for month and year.
 100
 101 This function is suitable for execution in a .emacs file."
 102   (interactive "P")
 103   (save-excursion
 104     (let* ((completion-ignore-case t)
 105            (date (if arg
 106                      (calendar-read-date t)
 107                    (calendar-current-date)))
 108            (displayed-month (extract-calendar-month date))
 109            (displayed-year (extract-calendar-year date)))
 110       (list-calendar-holidays))))
 111
 112 ;;;###autoload
 113 (defun list-holidays (y1 y2 &optional l label)
 114   "Display holidays for years Y1 to Y2 (inclusive).
 115
 116 The optional list of holidays L defaults to `calendar-holidays'.  See the
 117 documentation for that variable for a description of holiday lists.
 118
 119 The optional LABEL is used to label the buffer created."
 120   (interactive
 121    (let* ((start-year (calendar-read
 122                        "Starting year of holidays (>0): "
 123                        '(lambda (x) (> x 0))
 124                        (int-to-string (extract-calendar-year
 125                                        (calendar-current-date)))))
 126           (end-year (calendar-read
 127                        (format "Ending year (inclusive) of holidays (>=%s): "
 128                                start-year)
 129                        '(lambda (x) (>= x start-year))
 130                        (int-to-string start-year)))
 131           (completion-ignore-case t)
 132           (lists
 133            (list
 134             (cons "All" calendar-holidays)
 135             (if (fboundp 'atan)
 136                 (cons "Equinoxes/Solstices"
 137                       (list (list 'solar-equinoxes-solstices))))
 138             (if general-holidays (cons "General" general-holidays))
 139             (if local-holidays (cons "Local" local-holidays))
 140             (if other-holidays (cons "Other" other-holidays))
 141             (if christian-holidays (cons "Christian" christian-holidays))
 142             (if hebrew-holidays (cons "Hebrew" hebrew-holidays))
 143             (if islamic-holidays (cons "Islamic" islamic-holidays))
 144             (if oriental-holidays (cons "Oriental" oriental-holidays))
 145             (if solar-holidays (cons "Solar" solar-holidays))
 146             (cons "Ask" nil)))
 147           (choice (capitalize
 148                    (completing-read "List (TAB for choices): " lists nil t)))
 149           (which (if (string-equal choice "Ask")
 150                      (eval (read-variable "Enter list name: "))
 151                    (cdr (assoc choice lists))))
 152           (name (if (string-equal choice "Equinoxes/Solstices")
 153                     choice
 154                   (if (member choice '("Ask" ""))
 155                       "Holidays"
 156                     (format "%s Holidays" choice)))))
 157      (list start-year end-year which name)))
 158   (message "Computing holidays...")
 159   (let* ((holiday-buffer "*Holidays*")
 160          (calendar-holidays (if l l calendar-holidays))
 161          (title (or label "Holidays"))
 162          (holiday-list nil)
 163          (s (calendar-absolute-from-gregorian (list 2 1 y1)))
 164          (e (calendar-absolute-from-gregorian (list 11 1 y2)))
 165          (d s)
 166          (never t)
 167          (displayed-month 2)
 168          (displayed-year y1))
 169     (while (or never (<= d e))
 170       (setq holiday-list (append holiday-list (calendar-holiday-list)))
 171       (setq never nil)
 172       (increment-calendar-month displayed-month displayed-year 3)
 173       (setq d (calendar-absolute-from-gregorian
 174                (list displayed-month 1 displayed-year))))
 175     (save-excursion
 176       (set-buffer (get-buffer-create holiday-buffer))
 177       (setq buffer-read-only nil)
 178       (calendar-set-mode-line
 179        (if (= y1 y2)
 180            (format "%s for %s" title y1)
 181          (format "%s for %s-%s" title y1 y2)))
 182       (erase-buffer)
 183       (goto-char (point-min))
 184       (insert
 185        (mapconcat
 186         '(lambda (x) (concat (calendar-date-string (car x))
 187                              ": " (car (cdr x))))
 188         holiday-list "\n"))
 189       (goto-char (point-min))
 190       (set-buffer-modified-p nil)
 191       (setq buffer-read-only t)
 192       (display-buffer holiday-buffer)
 193       (message "Computing holidays...done"))))
 194
 195
 196 (defun check-calendar-holidays (date)
 197   "Check the list of holidays for any that occur on DATE.
 198 The value returned is a list of strings of relevant holiday descriptions.
 199 The holidays are those in the list calendar-holidays."
 200   (let* ((displayed-month (extract-calendar-month date))
 201          (displayed-year (extract-calendar-year date))
 202          (h (calendar-holiday-list))
 203          (holiday-list))
 204     (while h
 205       (if (calendar-date-equal date (car (car h)))
 206           (setq holiday-list (append holiday-list (cdr (car h)))))
 207       (setq h (cdr h)))
 208     holiday-list))
 209
 210 (defun calendar-cursor-holidays ()
 211   "Find holidays for the date specified by the cursor in the calendar window."
 212   (interactive)
 213   (message "Checking holidays...")
 214   (let* ((date (calendar-cursor-to-date t))
 215          (date-string (calendar-date-string date))
 216          (holiday-list (check-calendar-holidays date))
 217          (holiday-string (mapconcat 'identity holiday-list ";  "))
 218          (msg (format "%s:  %s" date-string holiday-string)))
 219     (if (not holiday-list)
 220         (message "No holidays known for %s" date-string)
 221       (if (<= (length msg) (frame-width))
 222           (message "%s" msg)
 223         (set-buffer (get-buffer-create holiday-buffer))
 224         (setq buffer-read-only nil)
 225         (calendar-set-mode-line date-string)
 226         (erase-buffer)
 227         (insert (mapconcat 'identity holiday-list "\n"))
 228         (goto-char (point-min))
 229         (set-buffer-modified-p nil)
 230         (setq buffer-read-only t)
 231         (display-buffer holiday-buffer)
 232         (message "Checking holidays...done")))))
 233
 234 (defun mark-calendar-holidays ()
 235   "Mark notable days in the calendar window."
 236   (interactive)
 237   (setq mark-holidays-in-calendar t)
 238   (message "Marking holidays...")
 239   (let ((holiday-list (calendar-holiday-list)))
 240     (while holiday-list
 241       (mark-visible-calendar-date
 242        (car (car holiday-list)) calendar-holiday-marker)
 243       (setq holiday-list (cdr holiday-list))))
 244   (message "Marking holidays...done"))
 245
 246 (defun list-calendar-holidays ()
 247   "Create a buffer containing the holidays for the current calendar window.
 248 The holidays are those in the list calendar-notable-days.  Returns t if any
 249 holidays are found, nil if not."
 250   (interactive)
 251   (message "Looking up holidays...")
 252   (let ((holiday-list (calendar-holiday-list))
 253         (m1 displayed-month)
 254         (y1 displayed-year)
 255         (m2 displayed-month)
 256         (y2 displayed-year))
 257     (if (not holiday-list)
 258         (progn
 259           (message "Looking up holidays...none found")
 260           nil)
 261       (set-buffer (get-buffer-create holiday-buffer))
 262       (setq buffer-read-only nil)
 263       (increment-calendar-month m1 y1 -1)
 264       (increment-calendar-month m2 y2 1)
 265       (calendar-set-mode-line
 266        (if (= y1 y2)
 267            (format "Notable Dates from %s to %s, %d%%-"
 268                    (calendar-month-name m1) (calendar-month-name m2) y2)
 269          (format "Notable Dates from %s, %d to %s, %d%%-"
 270                  (calendar-month-name m1) y1 (calendar-month-name m2) y2)))
 271       (erase-buffer)
 272       (insert
 273        (mapconcat
 274         '(lambda (x) (concat (calendar-date-string (car x))
 275                              ": " (car (cdr x))))
 276         holiday-list "\n"))
 277       (goto-char (point-min))
 278       (set-buffer-modified-p nil)
 279       (setq buffer-read-only t)
 280       (display-buffer holiday-buffer)
 281       (message "Looking up holidays...done")
 282       t)))
 283
 284 (defun calendar-holiday-list ()
 285   "Form the list of holidays that occur on dates in the calendar window.
 286 The holidays are those in the list calendar-holidays."
 287   (let ((p calendar-holidays)
 288         (holiday-list))
 289     (while p
 290       (let* ((holidays
 291               (if calendar-debug-sexp
 292                   (let ((stack-trace-on-error t))
 293                     (eval (car p)))
 294                 (condition-case nil
 295                     (eval (car p))
 296                   (error (beep)
 297                          (message "Bad holiday list item: %s" (car p))
 298                          (sleep-for 2))))))
 299         (if holidays
 300             (setq holiday-list (append holidays holiday-list))))
 301       (setq p (cdr p)))
 302     (setq holiday-list (sort holiday-list 'calendar-date-compare))))
 303
 304 ;; Below are the functions that calculate the dates of holidays; these
 305 ;; are eval'ed in the function calendar-holiday-list.  If you
 306 ;; write other such functions, be sure to imitate the style used below.
 307 ;; Remember that each function must return a list of items of the form
 308 ;; ((month day year) string) of VISIBLE dates in the calendar window.
 309
 310 (defun holiday-fixed (month day string)
 311   "Holiday on MONTH, DAY (Gregorian) called STRING.
 312 If MONTH, DAY is visible, the value returned is the list (((MONTH DAY year)
 313 STRING)).  Returns nil if it is not visible in the current calendar window."
 314   (let ((m displayed-month)
 315         (y displayed-year))
 316     (increment-calendar-month m y (- 11 month))
 317     (if (> m 9)
 318       (list (list (list month day y) string)))))
 319
 320 (defun holiday-float (month dayname n string &optional day)
 321   "Holiday on MONTH, DAYNAME (Nth occurrence) called STRING.
 322 If the Nth DAYNAME in MONTH is visible, the value returned is the list
 323 \(((MONTH DAY year) STRING)).
 324
 325 If N<0, count backward from the end of MONTH.
 326
 327 An optional parameter DAY means the Nth DAYNAME on or after/before MONTH DAY.
 328
 329 Returns nil if it is not visible in the current calendar window."
 330 ;; This is messy because the holiday may be visible, while the date on which
 331 ;; it is based is not.  For example, the first Monday after December 30 may be
 332 ;; visible when January is not.  For large values of |n| the problem is more
 333 ;; grotesque.  If we didn't have to worry about such cases, we could just use
 334
 335 ;;  (let ((m displayed-month)
 336 ;;        (y displayed-year))
 337 ;;    (increment-calendar-month m y (- 11 month))
 338 ;;    (if (> m 9); month in year y is visible
 339 ;;      (list (list (calendar-nth-named-day n dayname month y day) string)))))
 340
 341 ;; which is the way the function was originally written.
 342
 343   (let* ((m1 displayed-month)
 344          (y1 displayed-year)
 345          (m2 m1)
 346          (y2 y1))
 347     (increment-calendar-month m1 y1 -1)
 348     (increment-calendar-month m2 y2 1)
 349     (let* ((d1;  first possible base date for holiday
 350             (+ (calendar-nth-named-absday 1 dayname m1 y1)
 351                (* -7 n)
 352                (if (> n 0) 1 -7)))
 353            (d2;  last possible base date for holiday
 354             (+ (calendar-nth-named-absday -1 dayname m2 y2)
 355                (* -7 n)
 356                (if (> n 0) 7 -1)))
 357            (y1 (extract-calendar-year (calendar-gregorian-from-absolute d1)))
 358            (y2 (extract-calendar-year (calendar-gregorian-from-absolute d2)))
 359            (y; year of base date
 360             (if (or (= y1 y2) (> month 9))
 361                   y1
 362                 y2))
 363            (d; day of base date
 364             (or day (if (> n 0)
 365                         1
 366                       (calendar-last-day-of-month month y))))
 367            (date; base date for holiday
 368             (calendar-absolute-from-gregorian (list month d y))))
 369       (if (and (<= d1 date) (<= date d2))
 370           (list (list (calendar-nth-named-day n dayname month y d)
 371                       string))))))
 372
 373 (defun holiday-sexp (sexp string)
 374   "Sexp holiday for dates in the calendar window.
 375 SEXP is an expression in variable `year' evaluates to `date'.
 376
 377 STRING is an expression in `date' that evaluates to the holiday description
 378 of `date'.
 379
 380 If `date' is visible in the calendar window, the holiday STRING is on that
 381 date.  If date is nil, or if the date is not visible, there is no holiday."
 382   (let ((m displayed-month)
 383         (y displayed-year))
 384     (increment-calendar-month m y -1)
 385     (filter-visible-calendar-holidays
 386      (append
 387       (let* ((year y)
 388              (date (eval sexp))
 389              (string (if date (eval string))))
 390         (list (list date string)))
 391       (let* ((year (1+ y))
 392              (date (eval sexp))
 393              (string (if date (eval string))))
 394         (list (list date string)))))))
 395
 396 (defun holiday-advent ()
 397   "Date of Advent, if visible in calendar window."
 398   (let ((year displayed-year)
 399         (month displayed-month))
 400     (increment-calendar-month month year -1)
 401     (let ((advent (calendar-gregorian-from-absolute
 402                    (calendar-dayname-on-or-before 0
 403                     (calendar-absolute-from-gregorian
 404                      (list 12 3 year))))))
 405       (if (calendar-date-is-visible-p advent)
 406           (list (list advent "Advent"))))))
 407
 408 (defun holiday-easter-etc ()
 409   "List of dates related to Easter, as visible in calendar window."
 410  (if (and (> displayed-month 5) (not all-christian-calendar-holidays))
 411      nil;; Ash Wednesday, Good Friday, and Easter are not visible.
 412    (let* ((century (1+ (/ displayed-year 100)))
 413           (shifted-epact        ;; Age of moon for April 5...
 414            (% (+ 14 (* 11 (% displayed-year 19));;     ...by Nicaean rule
 415                  (-           ;; ...corrected for the Gregorian century rule
 416                   (/ (* 3 century) 4))
 417                  (/    ;; ...corrected for Metonic cycle inaccuracy.
 418                   (+ 5 (* 8 century)) 25)
 419                  (* 30 century));;              Keeps value positive.
 420               30))
 421           (adjusted-epact       ;;  Adjust for 29.5 day month.
 422            (if (or (= shifted-epact 0)
 423                    (and (= shifted-epact 1) (< 10 (% displayed-year 19))))
 424                (1+ shifted-epact)
 425              shifted-epact))
 426           (paschal-moon       ;; Day after the full moon on or after March 21.
 427            (- (calendar-absolute-from-gregorian (list 4 19 displayed-year))
 428               adjusted-epact))
 429           (abs-easter (calendar-dayname-on-or-before 0 (+ paschal-moon 7)))
 430           (mandatory
 431            (list
 432             (list (calendar-gregorian-from-absolute abs-easter)
 433                   "Easter Sunday")
 434             (list (calendar-gregorian-from-absolute (- abs-easter 2))
 435                   "Good Friday")
 436             (list (calendar-gregorian-from-absolute (- abs-easter 46))
 437                   "Ash Wednesday")))
 438           (optional
 439            (list
 440             (list (calendar-gregorian-from-absolute (- abs-easter 63))
 441                   "Septuagesima Sunday")
 442             (list (calendar-gregorian-from-absolute (- abs-easter 56))
 443                   "Sexagesima Sunday")
 444             (list (calendar-gregorian-from-absolute (- abs-easter 49))
 445                   "Shrove Sunday")
 446             (list (calendar-gregorian-from-absolute (- abs-easter 48))
 447                   "Shrove Monday")
 448             (list (calendar-gregorian-from-absolute (- abs-easter 47))
 449                   "Shrove Tuesday")
 450             (list (calendar-gregorian-from-absolute (- abs-easter 14))
 451                   "Passion Sunday")
 452             (list (calendar-gregorian-from-absolute (- abs-easter 7))
 453                   "Palm Sunday")
 454             (list (calendar-gregorian-from-absolute (- abs-easter 3))
 455                   "Maundy Thursday")
 456             (list (calendar-gregorian-from-absolute (+ abs-easter 35))
 457                   "Rogation Sunday")
 458             (list (calendar-gregorian-from-absolute (+ abs-easter 39))
 459                   "Ascension Day")
 460             (list (calendar-gregorian-from-absolute (+ abs-easter 49))
 461                   "Pentecost (Whitsunday)")
 462             (list (calendar-gregorian-from-absolute (+ abs-easter 50))
 463                   "Whitmonday")
 464             (list (calendar-gregorian-from-absolute (+ abs-easter 56))
 465                   "Trinity Sunday")
 466             (list (calendar-gregorian-from-absolute (+ abs-easter 60))
 467                   "Corpus Christi")))
 468           (output-list
 469            (filter-visible-calendar-holidays mandatory)))
 470      (if all-christian-calendar-holidays
 471          (setq output-list
 472                (append
 473                 (filter-visible-calendar-holidays optional)
 474                 output-list)))
 475      output-list)))
 476
 477 (defun holiday-greek-orthodox-easter ()
 478   "Date of Easter according to the rule of the Council of Nicaea."
 479   (let ((m displayed-month)
 480         (y displayed-year))
 481     (increment-calendar-month m y 1)
 482     (let* ((julian-year
 483             (extract-calendar-year
 484              (calendar-julian-from-absolute
 485               (calendar-absolute-from-gregorian
 486                (list m (calendar-last-day-of-month m y) y)))))
 487            (shifted-epact ;; Age of moon for April 5.
 488             (% (+ 14
 489                   (* 11 (% julian-year 19)))
 490                30))
 491            (paschal-moon  ;; Day after full moon on or after March 21.
 492             (- (calendar-absolute-from-julian (list 4 19 julian-year))
 493                shifted-epact))
 494            (nicaean-easter;; Sunday following the Paschal moon
 495             (calendar-gregorian-from-absolute
 496              (calendar-dayname-on-or-before 0 (+ paschal-moon 7)))))
 497       (if (calendar-date-is-visible-p nicaean-easter)
 498           (list (list nicaean-easter "Pascha (Greek Orthodox Easter)"))))))
 499
 500 (defun filter-visible-calendar-holidays (l)
 501   "Return a list of all visible holidays of those on L."
 502   (let ((visible)
 503         (p l))
 504     (while p
 505       (and (car (car p))
 506            (calendar-date-is-visible-p (car (car p)))
 507            (setq visible (append (list (car p)) visible)))
 508       (setq p (cdr p)))
 509     visible))
 510
 511 (provide 'holidays)
 512
 513 ;;; holidays.el ends here