lisp/calendar/holidays.el

   1 ;;; holidays.el --- holiday functions for the calendar package
   2
   3 ;; Copyright (C) 1989, 1990, 1992, 1993, 1994, 1997, 2001, 2002, 2003,
   4 ;;   2004, 2005, 2006, 2007, 2008  Free Software Foundation, Inc.
   5
   6 ;; Author: Edward M. Reingold <reingold@cs.uiuc.edu>
   7 ;; Maintainer: Glenn Morris <rgm@gnu.org>
   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 3, 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., 51 Franklin Street, Fifth Floor,
  25 ;; Boston, MA 02110-1301, 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: The Millennium Edition'' by Edward M. Reingold
  34 ;; and Nachum Dershowitz, Cambridge University Press (2001).
  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 ;;; Code:
  49
  50 (defvar displayed-month)
  51 (defvar displayed-year)
  52
  53 (require 'calendar)
  54
  55 (autoload 'holiday-julian "cal-julian"
  56   "Holiday on MONTH, DAY  (Julian) called STRING."
  57   t)
  58
  59 (autoload 'holiday-hebrew "cal-hebrew"
  60   "Holiday on MONTH, DAY (Hebrew) called STRING."
  61   t)
  62
  63 (autoload 'holiday-rosh-hashanah-etc "cal-hebrew"
  64   "List of dates related to Rosh Hashanah, as visible in calendar window."
  65   t)
  66
  67 (autoload 'holiday-hanukkah "cal-hebrew"
  68   "List of dates related to Hanukkah, as visible in calendar window."
  69   t)
  70
  71 (autoload 'holiday-passover-etc "cal-hebrew"
  72   "List of dates related to Passover, as visible in calendar window."
  73   t)
  74
  75 (autoload 'holiday-tisha-b-av-etc "cal-hebrew"
  76   "List of dates around Tisha B'Av, as visible in calendar window."
  77   t)
  78
  79 (autoload 'holiday-islamic "cal-islam"
  80   "Holiday on MONTH, DAY (Islamic) called STRING."
  81   t)
  82
  83 (autoload 'holiday-bahai "cal-bahai"
  84   "Holiday on MONTH, DAY (Baha'i) 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'.
 117 If you want to control what holidays are displayed, use a
 118 different list.  For example,
 119
 120   (list-holidays 2006 2006
 121     (append general-holidays local-holidays other-holidays))
 122
 123 will display holidays for the year 2006 defined in the 3
 124 mentioned lists, and nothing else.
 125
 126 When called interactively, this command offers a choice of
 127 holidays, based on the variables `solar-holidays' etc.  See the
 128 documentation of `calendar-holidays' for a list of the variables
 129 that control the choices, as well as a description of the format
 130 of a holiday list.
 131
 132 The optional LABEL is used to label the buffer created."
 133   (interactive
 134    (let* ((start-year (calendar-read
 135                        "Starting year of holidays (>0): "
 136                        '(lambda (x) (> x 0))
 137                        (int-to-string (extract-calendar-year
 138                                        (calendar-current-date)))))
 139           (end-year (calendar-read
 140                        (format "Ending year (inclusive) of holidays (>=%s): "
 141                                start-year)
 142                        '(lambda (x) (>= x start-year))
 143                        (int-to-string start-year)))
 144           (completion-ignore-case t)
 145           (lists
 146            (list
 147             (cons "All" calendar-holidays)
 148             (if (fboundp 'atan)
 149                 (cons "Equinoxes/Solstices"
 150                       (list (list 'solar-equinoxes-solstices))))
 151             (if general-holidays (cons "General" general-holidays))
 152             (if local-holidays (cons "Local" local-holidays))
 153             (if other-holidays (cons "Other" other-holidays))
 154             (if christian-holidays (cons "Christian" christian-holidays))
 155             (if hebrew-holidays (cons "Hebrew" hebrew-holidays))
 156             (if islamic-holidays (cons "Islamic" islamic-holidays))
 157             (if bahai-holidays (cons "Baha'i" bahai-holidays))
 158             (if oriental-holidays (cons "Oriental" oriental-holidays))
 159             (if solar-holidays (cons "Solar" solar-holidays))
 160             (cons "Ask" nil)))
 161           (choice (capitalize
 162                    (completing-read "List (TAB for choices): " lists nil t)))
 163           (which (if (string-equal choice "Ask")
 164                      (eval (read-variable "Enter list name: "))
 165                    (cdr (assoc choice lists))))
 166           (name (if (string-equal choice "Equinoxes/Solstices")
 167                     choice
 168                   (if (member choice '("Ask" ""))
 169                       "Holidays"
 170                     (format "%s Holidays" choice)))))
 171      (list start-year end-year which name)))
 172   (message "Computing holidays...")
 173   (let* ((holiday-buffer "*Holidays*")
 174          (calendar-holidays (if l l calendar-holidays))
 175          (title (or label "Holidays"))
 176          (holiday-list nil)
 177          (s (calendar-absolute-from-gregorian (list 2 1 y1)))
 178          (e (calendar-absolute-from-gregorian (list 11 1 y2)))
 179          (d s)
 180          (never t)
 181          (displayed-month 2)
 182          (displayed-year y1))
 183     (while (or never (<= d e))
 184       (setq holiday-list (append holiday-list (calendar-holiday-list)))
 185       (setq never nil)
 186       (increment-calendar-month displayed-month displayed-year 3)
 187       (setq d (calendar-absolute-from-gregorian
 188                (list displayed-month 1 displayed-year))))
 189     (save-excursion
 190       (set-buffer (get-buffer-create holiday-buffer))
 191       (setq buffer-read-only nil)
 192       (calendar-set-mode-line
 193        (if (= y1 y2)
 194            (format "%s for %s" title y1)
 195          (format "%s for %s-%s" title y1 y2)))
 196       (erase-buffer)
 197       (goto-char (point-min))
 198       (insert
 199        (mapconcat
 200         '(lambda (x) (concat (calendar-date-string (car x))
 201                              ": " (car (cdr x))))
 202         holiday-list "\n"))
 203       (goto-char (point-min))
 204       (set-buffer-modified-p nil)
 205       (setq buffer-read-only t)
 206       (display-buffer holiday-buffer)
 207       (message "Computing holidays...done"))))
 208
 209
 210 (defun check-calendar-holidays (date)
 211   "Check the list of holidays for any that occur on DATE.
 212 The value returned is a list of strings of relevant holiday descriptions.
 213 The holidays are those in the list calendar-holidays."
 214   (let* ((displayed-month (extract-calendar-month date))
 215          (displayed-year (extract-calendar-year date))
 216          (h (calendar-holiday-list))
 217          (holiday-list))
 218     (while h
 219       (if (calendar-date-equal date (car (car h)))
 220           (setq holiday-list (append holiday-list (cdr (car h)))))
 221       (setq h (cdr h)))
 222     holiday-list))
 223
 224 (defun calendar-cursor-holidays ()
 225   "Find holidays for the date specified by the cursor in the calendar window."
 226   (interactive)
 227   (message "Checking holidays...")
 228   (let* ((date (calendar-cursor-to-date t))
 229          (date-string (calendar-date-string date))
 230          (holiday-list (check-calendar-holidays date))
 231          (holiday-string (mapconcat 'identity holiday-list ";  "))
 232          (msg (format "%s:  %s" date-string holiday-string)))
 233     (if (not holiday-list)
 234         (message "No holidays known for %s" date-string)
 235       (if (<= (length msg) (frame-width))
 236           (message "%s" msg)
 237         (set-buffer (get-buffer-create holiday-buffer))
 238         (setq buffer-read-only nil)
 239         (calendar-set-mode-line date-string)
 240         (erase-buffer)
 241         (insert (mapconcat 'identity holiday-list "\n"))
 242         (goto-char (point-min))
 243         (set-buffer-modified-p nil)
 244         (setq buffer-read-only t)
 245         (display-buffer holiday-buffer)
 246         (message "Checking holidays...done")))))
 247
 248 (defun mark-calendar-holidays ()
 249   "Mark notable days in the calendar window."
 250   (interactive)
 251   (setq mark-holidays-in-calendar t)
 252   (message "Marking holidays...")
 253   (let ((holiday-list (calendar-holiday-list)))
 254     (while holiday-list
 255       (mark-visible-calendar-date
 256        (car (car holiday-list)) calendar-holiday-marker)
 257       (setq holiday-list (cdr holiday-list))))
 258   (message "Marking holidays...done"))
 259
 260 (defun list-calendar-holidays ()
 261   "Create a buffer containing the holidays for the current calendar window.
 262 The holidays are those in the list calendar-notable-days.  Returns t if any
 263 holidays are found, nil if not."
 264   (interactive)
 265   (message "Looking up holidays...")
 266   (let ((holiday-list (calendar-holiday-list))
 267         (m1 displayed-month)
 268         (y1 displayed-year)
 269         (m2 displayed-month)
 270         (y2 displayed-year))
 271     (if (not holiday-list)
 272         (progn
 273           (message "Looking up holidays...none found")
 274           nil)
 275       (set-buffer (get-buffer-create holiday-buffer))
 276       (setq buffer-read-only nil)
 277       (increment-calendar-month m1 y1 -1)
 278       (increment-calendar-month m2 y2 1)
 279       (calendar-set-mode-line
 280        (if (= y1 y2)
 281            (format "Notable Dates from %s to %s, %d%%-"
 282                    (calendar-month-name m1) (calendar-month-name m2) y2)
 283          (format "Notable Dates from %s, %d to %s, %d%%-"
 284                  (calendar-month-name m1) y1 (calendar-month-name m2) y2)))
 285       (erase-buffer)
 286       (insert
 287        (mapconcat
 288         '(lambda (x) (concat (calendar-date-string (car x))
 289                              ": " (car (cdr x))))
 290         holiday-list "\n"))
 291       (goto-char (point-min))
 292       (set-buffer-modified-p nil)
 293       (setq buffer-read-only t)
 294       (display-buffer holiday-buffer)
 295       (message "Looking up holidays...done")
 296       t)))
 297
 298 (defun calendar-holiday-list ()
 299   "Form the list of holidays that occur on dates in the calendar window.
 300 The holidays are those in the list calendar-holidays."
 301   (let ((p calendar-holidays)
 302         (holiday-list))
 303     (while p
 304       (let* ((holidays
 305               (if calendar-debug-sexp
 306                   (let ((stack-trace-on-error t))
 307                     (eval (car p)))
 308                 (condition-case nil
 309                     (eval (car p))
 310                   (error (beep)
 311                          (message "Bad holiday list item: %s" (car p))
 312                          (sleep-for 2))))))
 313         (if holidays
 314             (setq holiday-list (append holidays holiday-list))))
 315       (setq p (cdr p)))
 316     (setq holiday-list (sort holiday-list 'calendar-date-compare))))
 317
 318 ;; Below are the functions that calculate the dates of holidays; these
 319 ;; are eval'ed in the function calendar-holiday-list.  If you
 320 ;; write other such functions, be sure to imitate the style used below.
 321 ;; Remember that each function must return a list of items of the form
 322 ;; ((month day year) string) of VISIBLE dates in the calendar window.
 323
 324 (defun holiday-fixed (month day string)
 325   "Holiday on MONTH, DAY (Gregorian) called STRING.
 326 If MONTH, DAY is visible, the value returned is the list (((MONTH DAY year)
 327 STRING)).  Returns nil if it is not visible in the current calendar window."
 328   (let ((m displayed-month)
 329         (y displayed-year))
 330     (increment-calendar-month m y (- 11 month))
 331     (if (> m 9)
 332       (list (list (list month day y) string)))))
 333
 334 (defun holiday-float (month dayname n string &optional day)
 335   "Holiday on MONTH, DAYNAME (Nth occurrence) called STRING.
 336 If the Nth DAYNAME in MONTH is visible, the value returned is the list
 337 \(((MONTH DAY year) STRING)).
 338
 339 If N<0, count backward from the end of MONTH.
 340
 341 An optional parameter DAY means the Nth DAYNAME on or after/before MONTH DAY.
 342
 343 Returns nil if it is not visible in the current calendar window."
 344 ;; This is messy because the holiday may be visible, while the date on which
 345 ;; it is based is not.  For example, the first Monday after December 30 may be
 346 ;; visible when January is not.  For large values of |n| the problem is more
 347 ;; grotesque.  If we didn't have to worry about such cases, we could just use
 348
 349 ;;  (let ((m displayed-month)
 350 ;;        (y displayed-year))
 351 ;;    (increment-calendar-month m y (- 11 month))
 352 ;;    (if (> m 9); month in year y is visible
 353 ;;      (list (list (calendar-nth-named-day n dayname month y day) string)))))
 354
 355 ;; which is the way the function was originally written.
 356
 357   (let* ((m1 displayed-month)
 358          (y1 displayed-year)
 359          (m2 m1)
 360          (y2 y1))
 361     (increment-calendar-month m1 y1 -1)
 362     (increment-calendar-month m2 y2 1)
 363     (let* ((d1;  first possible base date for holiday
 364             (+ (calendar-nth-named-absday 1 dayname m1 y1)
 365                (* -7 n)
 366                (if (> n 0) 1 -7)))
 367            (d2;  last possible base date for holiday
 368             (+ (calendar-nth-named-absday -1 dayname m2 y2)
 369                (* -7 n)
 370                (if (> n 0) 7 -1)))
 371            (y1 (extract-calendar-year (calendar-gregorian-from-absolute d1)))
 372            (y2 (extract-calendar-year (calendar-gregorian-from-absolute d2)))
 373            (y; year of base date
 374             (if (or (= y1 y2) (> month 9))
 375                   y1
 376                 y2))
 377            (d; day of base date
 378             (or day (if (> n 0)
 379                         1
 380                       (calendar-last-day-of-month month y))))
 381            (date; base date for holiday
 382             (calendar-absolute-from-gregorian (list month d y))))
 383       (if (and (<= d1 date) (<= date d2))
 384           (list (list (calendar-nth-named-day n dayname month y d)
 385                       string))))))
 386
 387 (defun holiday-sexp (sexp string)
 388   "Sexp holiday for dates in the calendar window.
 389 SEXP is an expression in variable `year' evaluates to `date'.
 390
 391 STRING is an expression in `date' that evaluates to the holiday description
 392 of `date'.
 393
 394 If `date' is visible in the calendar window, the holiday STRING is on that
 395 date.  If date is nil, or if the date is not visible, there is no holiday."
 396   (let ((m displayed-month)
 397         (y displayed-year))
 398     (increment-calendar-month m y -1)
 399     (filter-visible-calendar-holidays
 400      (append
 401       (let* ((year y)
 402              (date (eval sexp))
 403              (string (if date (eval string))))
 404         (list (list date string)))
 405       (let* ((year (1+ y))
 406              (date (eval sexp))
 407              (string (if date (eval string))))
 408         (list (list date string)))))))
 409
 410 (defun holiday-advent (&optional n string)
 411   "Date of Nth day after advent (named STRING), if visible in calendar window.
 412 Negative values of N are interpreted as days before advent.
 413 STRING is used purely for display purposes.  The return value has
 414 the form ((MONTH DAY YEAR) STRING), where the date is that of the
 415 Nth day before or after advent.
 416
 417 For backwards compatibility, if this function is called with no
 418 arguments, then it returns the value appropriate for advent itself."
 419   ;; Backwards compatibility layer.
 420   (if (not n)
 421       (holiday-advent 0 "Advent")
 422     (let ((year displayed-year)
 423           (month displayed-month))
 424       (increment-calendar-month month year -1)
 425       (let ((advent (calendar-gregorian-from-absolute
 426                      (+ n
 427                         (calendar-dayname-on-or-before
 428                          0
 429                          (calendar-absolute-from-gregorian
 430                           (list 12 3 year)))))))
 431         (if (calendar-date-is-visible-p advent)
 432             (list (list advent string)))))))
 433
 434 (defun holiday-easter-etc (&optional n string)
 435   "Date of Nth day after Easter (named STRING), if visible in calendar window.
 436 Negative values of N are interpreted as days before Easter.
 437 STRING is used purely for display purposes.  The return value has
 438 the form ((MONTH DAY YEAR) STRING), where the date is that of the
 439 Nth day before or after Easter.
 440
 441 For backwards compatibility, if this function is called with no
 442 arguments, then it returns a list of \"standard\" Easter-related
 443 holidays (with more entries if `all-christian-calendar-holidays'
 444 is non-nil)."
 445   ;; Backwards compatibility layer.
 446   (if (not n)
 447       (let (res-list res)
 448         (dolist (elem (append
 449                        (if all-christian-calendar-holidays
 450                            '((-63 . "Septuagesima Sunday")
 451                              (-56 . "Sexagesima Sunday")
 452                              (-49 . "Shrove Sunday")
 453                              (-48 . "Shrove Monday")
 454                              (-47 . "Shrove Tuesday")
 455                              (-14 . "Passion Sunday")
 456                              (-7 . "Palm Sunday")
 457                              (-3 . "Maundy Thursday")
 458                              (35 . "Rogation Sunday")
 459                              (39 . "Ascension Day")
 460                              (49 . "Pentecost (Whitsunday)")
 461                              (50 . "Whitmonday")
 462                              (56 . "Trinity Sunday")
 463                              (60 . "Corpus Christi")))
 464                        '((0 . "Easter Sunday")
 465                          (-2 . "Good Friday")
 466                          (-46 . "Ash Wednesday")))
 467                       res-list)
 468           ;; Filter out nil (not visible) values.
 469           (if (setq res (holiday-easter-etc (car elem) (cdr elem)))
 470               (setq res-list (append res res-list)))))
 471     (let* ((century (1+ (/ displayed-year 100)))
 472            (shifted-epact ;; Age of moon for April 5...
 473             (% (+ 14 (* 11 (% displayed-year 19)) ;;     ...by Nicaean rule
 474                   (- ;; ...corrected for the Gregorian century rule
 475                    (/ (* 3 century) 4))
 476                   (/ ;; ...corrected for Metonic cycle inaccuracy.
 477                    (+ 5 (* 8 century)) 25)
 478                   (* 30 century)) ;;              Keeps value positive.
 479                30))
 480            (adjusted-epact ;;  Adjust for 29.5 day month.
 481             (if (or (zerop shifted-epact)
 482                     (and (= shifted-epact 1) (< 10 (% displayed-year 19))))
 483                 (1+ shifted-epact)
 484               shifted-epact))
 485            (paschal-moon ;; Day after the full moon on or after March 21.
 486             (- (calendar-absolute-from-gregorian (list 4 19 displayed-year))
 487                adjusted-epact))
 488            (abs-easter (calendar-dayname-on-or-before 0 (+ paschal-moon 7))))
 489       (filter-visible-calendar-holidays
 490        (list (list (calendar-gregorian-from-absolute (+ abs-easter n))
 491                    string))))))
 492
 493 (defun holiday-greek-orthodox-easter ()
 494   "Date of Easter according to the rule of the Council of Nicaea."
 495   (let ((m displayed-month)
 496         (y displayed-year))
 497     (increment-calendar-month m y 1)
 498     (let* ((julian-year
 499             (extract-calendar-year
 500              (calendar-julian-from-absolute
 501               (calendar-absolute-from-gregorian
 502                (list m (calendar-last-day-of-month m y) y)))))
 503            (shifted-epact ;; Age of moon for April 5.
 504             (% (+ 14
 505                   (* 11 (% julian-year 19)))
 506                30))
 507            (paschal-moon  ;; Day after full moon on or after March 21.
 508             (- (calendar-absolute-from-julian (list 4 19 julian-year))
 509                shifted-epact))
 510            (nicaean-easter;; Sunday following the Paschal moon
 511             (calendar-gregorian-from-absolute
 512              (calendar-dayname-on-or-before 0 (+ paschal-moon 7)))))
 513       (if (calendar-date-is-visible-p nicaean-easter)
 514           (list (list nicaean-easter "Pascha (Greek Orthodox Easter)"))))))
 515
 516 (defun filter-visible-calendar-holidays (l)
 517   "Return a list of all visible holidays of those on L."
 518   (let ((visible)
 519         (p l))
 520     (while p
 521       (and (car (car p))
 522            (calendar-date-is-visible-p (car (car p)))
 523            (setq visible (append (list (car p)) visible)))
 524       (setq p (cdr p)))
 525     visible))
 526
 527 (provide 'holidays)
 528
 529 ;;; arch-tag: 48eb3117-75a7-4dbe-8fd9-873c3cbb0d37
 530 ;;; holidays.el ends here