lisp/calendar/holidays.el

   1 ;;; holidays.el --- holiday functions for the calendar package
   2
   3 ;; Copyright (C) 1989, 1990, 1991 Free Software Foundation, Inc.
   4
   5 ;; This file is part of GNU Emacs.
   6
   7 ;; GNU Emacs is distributed in the hope that it will be useful,
   8 ;; but WITHOUT ANY WARRANTY.  No author or distributor
   9 ;; accepts responsibility to anyone for the consequences of using it
  10 ;; or for whether it serves any particular purpose or works at all,
  11 ;; unless he says so in writing.  Refer to the GNU Emacs General Public
  12 ;; License for full details.
  13
  14 ;; Everyone is granted permission to copy, modify and redistribute
  15 ;; GNU Emacs, but only under the conditions described in the
  16 ;; GNU Emacs General Public License.   A copy of this license is
  17 ;; supposed to have been given to you along with GNU Emacs so you
  18 ;; can know your rights and responsibilities.  It should be in a
  19 ;; file named COPYING.  Among other things, the copyright notice
  20 ;; and this notice must be preserved on all copies.
  21
  22 ;; This collection of functions implements the holiday features as described
  23 ;; in calendar.el.
  24
  25 ;; Comments, corrections, and improvements should be sent to
  26 ;;  Edward M. Reingold               Department of Computer Science
  27 ;;  (217) 333-6733                   University of Illinois at Urbana-Champaign
  28 ;;  reingold@cs.uiuc.edu             1304 West Springfield Avenue
  29 ;;                                   Urbana, Illinois 61801
  30
  31 ;; Technical details of all the calendrical calculations can be found in
  32 ;; ``Calendrical Calculations'' by Nachum Dershowitz and Edward M. Reingold,
  33 ;; Software--Practice and Experience, Volume 20, Number 9 (September, 1990),
  34 ;; pages 899-928.
  35
  36 (require 'calendar)
  37 (defun holidays ()
  38   "Display the holidays for last month, this month, and next month.
  39 This function is suitable for execution in a .emacs file."
  40   (interactive)
  41   (save-excursion
  42     (let* ((date (calendar-current-date))
  43            (displayed-month (extract-calendar-month date))
  44            (displayed-year (extract-calendar-year date)))
  45       (list-calendar-holidays))))
  46
  47 (defun check-calendar-holidays (date)
  48   "Check the list of holidays for any that occur on DATE.
  49 The value returned is a list of strings of relevant holiday descriptions.
  50 The holidays are those in the list calendar-holidays."
  51   (let* ((displayed-month (extract-calendar-month date))
  52          (displayed-year (extract-calendar-year date))
  53          (h (calendar-holiday-list))
  54          (holiday-list))
  55     (while h
  56       (if (calendar-date-equal date (car (car h)))
  57           (setq holiday-list (append holiday-list (cdr (car h)))))
  58       (setq h (cdr h)))
  59     holiday-list))
  60
  61 (defun calendar-cursor-holidays ()
  62   "Find holidays for the date specified by the cursor in the calendar window."
  63   (interactive)
  64   (message "Checking holidays...")
  65   (let* ((date (calendar-cursor-to-date))
  66          (date-string (calendar-date-string date))
  67          (holiday-list (check-calendar-holidays date))
  68          (holiday-string (mapconcat 'identity holiday-list ";  "))
  69          (msg (format "%s:  %s" date-string holiday-string)))
  70     (if (not holiday-list)
  71         (message "No holidays known for %s" date-string)
  72       (if (<= (length msg) (screen-width))
  73           (message msg)
  74         (set-buffer (get-buffer-create holiday-buffer))
  75         (setq buffer-read-only nil)
  76         (setq mode-line-format
  77               (format "--------------------------%s%%-"
  78                       date-string))
  79         (erase-buffer)
  80         (insert (mapconcat 'identity holiday-list "\n"))
  81         (goto-char (point-min))
  82         (set-buffer-modified-p nil)
  83         (setq buffer-read-only t)
  84         (display-buffer holiday-buffer)
  85         (message "Checking holidays...done")))))
  86
  87 (defun mark-calendar-holidays ()
  88   "Mark notable days in the calendar window."
  89   (interactive)
  90   (setq mark-holidays-in-calendar t)
  91   (message "Marking holidays...")
  92   (let ((holiday-list (calendar-holiday-list)))
  93     (while holiday-list
  94       (mark-visible-calendar-date
  95        (car (car holiday-list)) calendar-holiday-marker)
  96       (setq holiday-list (cdr holiday-list))))
  97   (message "Marking holidays...done"))
  98
  99 (defun list-calendar-holidays ()
 100   "Create a buffer containing the holidays for the current calendar window.
 101 The holidays are those in the list calendar-notable-days.  Returns t if any
 102 holidays are found, nil if not."
 103   (interactive)
 104   (message "Looking up holidays...")
 105   (let ((holiday-list (calendar-holiday-list))
 106         (m1 displayed-month)
 107         (y1 displayed-year)
 108         (m2 displayed-month)
 109         (y2 displayed-year))
 110     (if (not holiday-list)
 111         (progn
 112           (message "Looking up holidays...none found")
 113           nil)
 114       (set-buffer (get-buffer-create holiday-buffer))
 115       (setq buffer-read-only nil)
 116       (increment-calendar-month m1 y1 -1)
 117       (increment-calendar-month m2 y2 1)
 118       (setq mode-line-format
 119             (format "-------------Notable Dates from %s, %d to %s, %d%%-"
 120                     (calendar-month-name m1) y1 (calendar-month-name m2) y2))
 121       (erase-buffer)
 122       (insert
 123        (mapconcat
 124         '(lambda (x) (concat (calendar-date-string (car x))
 125                              ": " (car (cdr x))))
 126         holiday-list "\n"))
 127       (goto-char (point-min))
 128       (set-buffer-modified-p nil)
 129       (setq buffer-read-only t)
 130       (display-buffer holiday-buffer)
 131       (message "Looking up holidays...done")
 132       t)))
 133
 134 (defun calendar-holiday-list ()
 135   "Form the list of holidays that occur on dates in the calendar window.
 136 The holidays are those in the list calendar-holidays."
 137   (let ((p calendar-holidays)
 138         (holiday-list))
 139     (while p
 140       (let* ((function-name
 141               (intern (format "calendar-holiday-function-%s" (car (car p)))))
 142              (holidays
 143               (if (cdr (car p));; optional arguments
 144                   (funcall function-name (cdr (car p)))
 145                 (funcall function-name))))
 146         (if holidays
 147             (setq holiday-list (append holidays holiday-list))))
 148       (setq p (cdr p)))
 149     (setq holiday-list (sort holiday-list 'calendar-date-compare))))
 150
 151 ;; Below are the functions that calculate the dates of holidays; these
 152 ;; are called by the funcall in the function calendar-holiday-list.  If you
 153 ;; write other such functions, be sure to imitate the style used below,
 154 ;; including the evaluation of each element in the list that constitutes
 155 ;; the argument to the function.  If you don't do this evaluation, the
 156 ;; list calendar-holidays cannot contain expressions (as, for example, in
 157 ;; the entry for the Islamic new year.  Also remember that each function
 158 ;; must return a list of items of the form ((month day year) string);
 159 ;; the date (month day year) should be visible in the calendar window.
 160
 161 (defun calendar-holiday-function-fixed (x)
 162   "Returns the corresponding Gregorian date, if visible in the window, to
 163 month, year where month is (car X) and year is (car (cdr X)).  If it is
 164 visible, the value returned is the list (((month day year) string)) where
 165 string is (car (nthcdr 2 X)).  Returns nil if it is not visible in the
 166 current calendar window."
 167   (let* ((month (eval (car x)))
 168          (day (eval (car (cdr x))))
 169          (string (eval (car (nthcdr 2 x))))
 170          (m displayed-month)
 171          (y displayed-year))
 172     (increment-calendar-month m y (- 11 month))
 173     (if (> m 9)
 174       (list (list (list month day y) string)))))
 175
 176 (defun calendar-holiday-function-float (x)
 177   "Returns the corresponding Gregorian date, if visible in the window, to the
 178 n-th occurrence (negative counts from the end of the month) of dayname in
 179 month, year where month is (car X), year is (car (cdr X)), n is
 180 \(car \(nthcdr 2 X\)\).  If it is visible, the value returned is the list
 181 \(\(\(month day year)\ string\)\) where string is (car (nthcdr 3 X)).
 182 Returns nil if it is not visible in the current calendar window."
 183   (let* ((month (eval (car x)))
 184          (dayname (eval (car (cdr x))))
 185          (n (eval (car (nthcdr 2 x))))
 186          (string (eval (car (nthcdr 3 x))))
 187          (m displayed-month)
 188          (y displayed-year))
 189     (increment-calendar-month m y (- 11 month))
 190     (if (> m 9)
 191       (list (list (calendar-nth-named-day n dayname month y) string)))))
 192
 193 (defun calendar-holiday-function-julian (x)
 194   "Returns the corresponding Gregorian date, if visible in the window, to the
 195 Julian date month, year where month is (car X) and year is (car (cdr X)).
 196 If it is visible, the value returned is the list (((month day year) string))
 197 where string is (car (nthcdr 2 X)).  Returns nil if it is not visible in the
 198 current calendar window."
 199   (let* ((month (eval (car x)))
 200          (day (eval (car (cdr x))))
 201          (string (eval (car (nthcdr 2 x))))
 202          (m1 displayed-month)
 203          (y1 displayed-year)
 204          (m2 displayed-month)
 205          (y2 displayed-year)
 206          (year))
 207     (increment-calendar-month m1 y1 -1)
 208     (increment-calendar-month m2 y2 1)
 209     (let* ((start-date (calendar-absolute-from-gregorian
 210                         (list m1 1 y1)))
 211            (end-date (calendar-absolute-from-gregorian
 212                       (list m2 (calendar-last-day-of-month m2 y2) y2)))
 213            (julian-start (calendar-julian-from-absolute start-date))
 214            (julian-end (calendar-julian-from-absolute end-date))
 215            (julian-y1 (extract-calendar-year julian-start))
 216            (julian-y2 (extract-calendar-year julian-end)))
 217       (setq year (if (< 10 month) julian-y1 julian-y2))
 218       (let ((date (calendar-gregorian-from-absolute
 219                    (calendar-absolute-from-julian
 220                     (list month day year)))))
 221         (if (calendar-date-is-visible-p date)
 222             (list (list date string)))))))
 223
 224 (defun calendar-holiday-function-islamic (x)
 225   "Returns the corresponding Gregorian date, if visible in the window, to the
 226 Islamic date month, day where month is (car X) and day is (car (cdr X)).
 227 If it is visible, the value returned is the list (((month day year) string))
 228 where string is (car (nthcdr 2 X)).  Returns nil if it is not visible in
 229 the current calendar window."
 230   (let* ((month (eval (car x)))
 231          (day (eval (car (cdr x))))
 232          (string (eval (car (nthcdr 2 x))))
 233          (islamic-date (calendar-islamic-from-absolute
 234                         (calendar-absolute-from-gregorian
 235                          (list displayed-month 15 displayed-year))))
 236          (m (extract-calendar-month islamic-date))
 237          (y (extract-calendar-year islamic-date))
 238         (date))
 239     (if (< m 1)
 240         nil;;   Islamic calendar doesn't apply.
 241       (increment-calendar-month m y (- 10 month))
 242       (if (> m 7);;  Islamic date might be visible
 243           (let ((date (calendar-gregorian-from-absolute
 244                        (calendar-absolute-from-islamic (list month day y)))))
 245             (if (calendar-date-is-visible-p date)
 246                 (list (list date string))))))))
 247
 248 (defun calendar-holiday-function-hebrew (x)
 249   "Returns the corresponding Gregorian date, if visible in the window, to the
 250 Hebrew date month, day where month is (car X) and day is (car (cdr X)).
 251 If it is visible, the value returned is the list (((month day year) string))
 252 where string is (car (nthcdr 2 X)).  Returns nil if it is not visible in
 253 the current calendar window."
 254   (let* ((month (eval (car x)))
 255          (day (eval (car (cdr x))))
 256          (string (eval (car (nthcdr 2 x)))))
 257     (if (memq displayed-month;;  This test is only to speed things up a bit;
 258               (list          ;;  it works fine without the test too.
 259                (if (< 11 month) (- month 11) (+ month 1))
 260                (if (< 10 month) (- month 10) (+ month 2))
 261                (if (<  9 month) (- month  9) (+ month 3))
 262                (if (<  8 month) (- month  8) (+ month 4))
 263                (if (<  7 month) (- month  7) (+ month 5))))
 264         (let ((m1 displayed-month)
 265               (y1 displayed-year)
 266               (m2 displayed-month)
 267               (y2 displayed-year)
 268               (year))
 269           (increment-calendar-month m1 y1 -1)
 270           (increment-calendar-month m2 y2 1)
 271           (let* ((start-date (calendar-absolute-from-gregorian
 272                               (list m1 1 y1)))
 273                  (end-date (calendar-absolute-from-gregorian
 274                             (list m2 (calendar-last-day-of-month m2 y2) y2)))
 275                  (hebrew-start (calendar-hebrew-from-absolute start-date))
 276                  (hebrew-end (calendar-hebrew-from-absolute end-date))
 277                  (hebrew-y1 (extract-calendar-year hebrew-start))
 278                  (hebrew-y2 (extract-calendar-year hebrew-end)))
 279             (setq year (if (< 6 month) hebrew-y2 hebrew-y1))
 280             (let ((date (calendar-gregorian-from-absolute
 281                          (calendar-absolute-from-hebrew
 282                           (list month day year)))))
 283               (if (calendar-date-is-visible-p date)
 284                   (list (list date string)))))))))
 285
 286 (defun calendar-holiday-function-if (x)
 287   "Conditional holiday for dates in the calendar window.
 288 The boolean condition is (car X).  If t, the holiday (car (cdr X)) is
 289 checked.  If nil, the holiday (car (cdr (cdr X))), if there, is checked."
 290   (let* ((boolean (eval (car x)))
 291          (h (if boolean (car (cdr x)) (car (cdr (cdr x))))))
 292     (if h
 293      (let* ((function-name
 294               (intern (format "calendar-holiday-function-%s" (car h))))
 295             (holidays
 296               (if (cdr h);; optional arguments
 297                   (funcall function-name (cdr h))
 298                 (funcall function-name))))
 299        holidays))))
 300
 301 (defun calendar-holiday-function-advent ()
 302   "Date of Advent, if visible in calendar window."
 303   (let ((year displayed-year)
 304         (month displayed-month))
 305     (increment-calendar-month month year -1)
 306     (let ((advent (calendar-gregorian-from-absolute
 307                    (calendar-dayname-on-or-before 0
 308                     (calendar-absolute-from-gregorian
 309                      (list 12 3 year))))))
 310       (if (calendar-date-is-visible-p advent)
 311           (list (list advent "Advent"))))))
 312
 313 (defun calendar-holiday-function-easter-etc ()
 314   "List of dates related to Easter, as visible in calendar window."
 315  (if (and (> displayed-month 5) (not all-christian-calendar-holidays))
 316      nil;; Ash Wednesday, Good Friday, and Easter are not visible.
 317    (let* ((century (1+ (/ displayed-year 100)))
 318           (shifted-epact        ;; Age of moon for April 5...
 319            (% (+ 14 (* 11 (% displayed-year 19));;     ...by Nicaean rule
 320                  (-           ;; ...corrected for the Gregorian century rule
 321                   (/ (* 3 century) 4))
 322                  (/    ;; ...corrected for Metonic cycle inaccuracy.
 323                   (+ 5 (* 8 century)) 25)
 324                  (* 30 century));;              Keeps value positive.
 325               30))
 326           (adjusted-epact       ;;  Adjust for 29.5 day month.
 327            (if (or (= shifted-epact 0)
 328                    (and (= shifted-epact 1) (< 10 (% displayed-year 19))))
 329                (1+ shifted-epact)
 330              shifted-epact))
 331           (paschal-moon       ;; Day after the full moon on or after March 21.
 332            (- (calendar-absolute-from-gregorian (list 4 19 displayed-year))
 333               adjusted-epact))
 334           (abs-easter (calendar-dayname-on-or-before 0 (+ paschal-moon 7)))
 335           (mandatory
 336            (list
 337             (list (calendar-gregorian-from-absolute abs-easter)
 338                   "Easter Sunday")
 339             (list (calendar-gregorian-from-absolute (- abs-easter 2))
 340                   "Good Friday")
 341             (list (calendar-gregorian-from-absolute (- abs-easter 46))
 342                   "Ash Wednesday")))
 343           (optional
 344            (list
 345             (list (calendar-gregorian-from-absolute (- abs-easter 63))
 346                   "Septuagesima Sunday")
 347             (list (calendar-gregorian-from-absolute (- abs-easter 56))
 348                   "Sexagesima Sunday")
 349             (list (calendar-gregorian-from-absolute (- abs-easter 49))
 350                   "Shrove Sunday")
 351             (list (calendar-gregorian-from-absolute (- abs-easter 48))
 352                   "Shrove Monday")
 353             (list (calendar-gregorian-from-absolute (- abs-easter 47))
 354                   "Shrove Tuesday")
 355             (list (calendar-gregorian-from-absolute (- abs-easter 14))
 356                   "Passion Sunday")
 357             (list (calendar-gregorian-from-absolute (- abs-easter 7))
 358                   "Palm Sunday")
 359             (list (calendar-gregorian-from-absolute (- abs-easter 3))
 360                   "Maundy Thursday")
 361             (list (calendar-gregorian-from-absolute (+ abs-easter 35))
 362                   "Rogation Sunday")
 363             (list (calendar-gregorian-from-absolute (+ abs-easter 39))
 364                   "Ascension Sunday")
 365             (list (calendar-gregorian-from-absolute (+ abs-easter 49))
 366                   "Pentecost (Whitsunday)")
 367             (list (calendar-gregorian-from-absolute (+ abs-easter 50))
 368                   "Whitmunday")
 369             (list (calendar-gregorian-from-absolute (+ abs-easter 56))
 370                   "Trinity Sunday")
 371             (list (calendar-gregorian-from-absolute (+ abs-easter 60))
 372                   "Corpus Christi")))
 373           (output-list
 374            (filter-visible-calendar-holidays mandatory)))
 375      (if all-christian-calendar-holidays
 376          (setq output-list
 377                (append
 378                 (filter-visible-calendar-holidays optional)
 379                 output-list)))
 380      output-list)))
 381
 382 (defun calendar-holiday-function-rosh-hashanah-etc ()
 383   "List of dates related to Rosh Hashanah, as visible in calendar window."
 384   (if (or (< displayed-month 8)
 385           (> displayed-month 11))
 386       nil;; None of the dates is visible
 387     (let* ((abs-r-h (calendar-absolute-from-hebrew
 388                       (list 7 1 (+ displayed-year 3761))))
 389             (mandatory
 390              (list
 391               (list (calendar-gregorian-from-absolute abs-r-h)
 392                     (format "Rosh HaShanah %d" (+ 3761 displayed-year)))
 393               (list (calendar-gregorian-from-absolute (+ abs-r-h 9))
 394                     "Yom Kippur")
 395               (list (calendar-gregorian-from-absolute (+ abs-r-h 14))
 396                     "Sukkot")
 397               (list (calendar-gregorian-from-absolute (+ abs-r-h 21))
 398                     "Shemini Atzeret")
 399               (list (calendar-gregorian-from-absolute (+ abs-r-h 22))
 400                     "Simchat Torah")))
 401            (optional
 402             (list
 403              (list (calendar-gregorian-from-absolute
 404                     (calendar-dayname-on-or-before 6 (- abs-r-h 4)))
 405                    "Selichot (night)")
 406              (list (calendar-gregorian-from-absolute (1- abs-r-h))
 407                    "Erev Rosh HaShannah")
 408              (list (calendar-gregorian-from-absolute (1+ abs-r-h))
 409                    "Rosh HaShanah (second day)")
 410              (list (calendar-gregorian-from-absolute
 411                     (if (= (% abs-r-h 7) 4) (+ abs-r-h 3) (+ abs-r-h 2)))
 412                    "Tzom Gedaliah")
 413              (list (calendar-gregorian-from-absolute
 414                     (calendar-dayname-on-or-before 6 (+ 7 abs-r-h)))
 415                    "Shabbat Shuvah")
 416              (list (calendar-gregorian-from-absolute (+ abs-r-h 8))
 417                    "Erev Yom Kippur")
 418              (list (calendar-gregorian-from-absolute (+ abs-r-h 13))
 419                    "Erev Sukkot")
 420              (list (calendar-gregorian-from-absolute (+ abs-r-h 15))
 421                    "Sukkot (second day)")
 422              (list (calendar-gregorian-from-absolute (+ abs-r-h 16))
 423                    "Hol Hamoed Sukkot (first day)")
 424              (list (calendar-gregorian-from-absolute (+ abs-r-h 17))
 425                    "Hol Hamoed Sukkot (second day)")
 426              (list (calendar-gregorian-from-absolute (+ abs-r-h 18))
 427                    "Hol Hamoed Sukkot (third day)")
 428              (list (calendar-gregorian-from-absolute (+ abs-r-h 19))
 429                    "Hol Hamoed Sukkot (fourth day)")
 430              (list (calendar-gregorian-from-absolute (+ abs-r-h 20))
 431                    "Hoshannah Rabbah")))
 432             (output-list
 433              (filter-visible-calendar-holidays mandatory)))
 434       (if all-hebrew-calendar-holidays
 435           (setq output-list
 436                 (append
 437                  (filter-visible-calendar-holidays optional)
 438                  output-list)))
 439       output-list)))
 440
 441 (defun calendar-holiday-function-hanukkah ()
 442   "List of dates related to Hanukkah, as visible in calendar window."
 443     (if (memq displayed-month;;  This test is only to speed things up a bit;
 444               '(10 11 12 1 2));; it works fine without the test too.
 445         (let ((m displayed-month)
 446               (y displayed-year))
 447           (increment-calendar-month m y 1)
 448           (let* ((h-y (extract-calendar-year
 449                          (calendar-hebrew-from-absolute
 450                           (calendar-absolute-from-gregorian
 451                            (list m (calendar-last-day-of-month m y) y)))))
 452                  (abs-h (calendar-absolute-from-hebrew (list 9 25 h-y))))
 453             (filter-visible-calendar-holidays
 454              (list
 455               (list (calendar-gregorian-from-absolute (1- abs-h))
 456                     "Erev Hanukkah")
 457               (list (calendar-gregorian-from-absolute abs-h)
 458                     "Hanukkah (first day)")
 459               (list (calendar-gregorian-from-absolute (1+ abs-h))
 460                     "Hanukkah (second day)")
 461               (list (calendar-gregorian-from-absolute (+ abs-h 2))
 462                     "Hanukkah (third day)")
 463               (list (calendar-gregorian-from-absolute (+ abs-h 3))
 464                     "Hanukkah (fourth day)")
 465               (list (calendar-gregorian-from-absolute (+ abs-h 4))
 466                     "Hanukkah (fifth day)")
 467               (list (calendar-gregorian-from-absolute (+ abs-h 5))
 468                     "Hanukkah (sixth day)")
 469               (list (calendar-gregorian-from-absolute (+ abs-h 6))
 470                     "Hanukkah (seventh day)")
 471               (list (calendar-gregorian-from-absolute (+ abs-h 7))
 472                     "Hanukkah (eighth day)")))))))
 473
 474 (defun calendar-holiday-function-passover-etc ()
 475   "List of dates related to Passover, as visible in calendar window."
 476  (if (< 7 displayed-month)
 477       nil;; None of the dates is visible
 478     (let* ((abs-p (calendar-absolute-from-hebrew
 479                       (list 1 15 (+ displayed-year 3760))))
 480            (mandatory
 481             (list
 482              (list (calendar-gregorian-from-absolute abs-p)
 483                    "Passover")
 484              (list (calendar-gregorian-from-absolute (+ abs-p 50))
 485                    "Shavuot")))
 486            (optional
 487             (list
 488              (list (calendar-gregorian-from-absolute
 489                     (calendar-dayname-on-or-before 6 (- abs-p 43)))
 490                    "Shabbat Shekalim")
 491              (list (calendar-gregorian-from-absolute
 492                     (calendar-dayname-on-or-before 6 (- abs-p 30)))
 493                    "Shabbat Zachor")
 494              (list (calendar-gregorian-from-absolute
 495                     (if (= (% abs-p 7) 2) (- abs-p 33) (- abs-p 31)))
 496                    "Fast of Esther")
 497              (list (calendar-gregorian-from-absolute (- abs-p 31))
 498                    "Erev Purim")
 499              (list (calendar-gregorian-from-absolute (- abs-p 30))
 500                    "Purim")
 501              (list (calendar-gregorian-from-absolute
 502                     (if (zerop (% abs-p 7)) (- abs-p 28) (- abs-p 29)))
 503                    "Shushan Purim")
 504              (list (calendar-gregorian-from-absolute
 505                     (- (calendar-dayname-on-or-before 6 (- abs-p 14)) 7))
 506                    "Shabbat Parah")
 507              (list (calendar-gregorian-from-absolute
 508                     (calendar-dayname-on-or-before 6 (- abs-p 14)))
 509                    "Shabbat HaHodesh")
 510              (list (calendar-gregorian-from-absolute
 511                     (calendar-dayname-on-or-before 6 (1- abs-p)))
 512                    "Shabbat HaGadol")
 513              (list (calendar-gregorian-from-absolute (1- abs-p))
 514                    "Erev Passover")
 515              (list (calendar-gregorian-from-absolute (1+ abs-p))
 516                    "Passover (second day)")
 517              (list (calendar-gregorian-from-absolute (+ abs-p 2))
 518                    "Hol Hamoed Passover (first day)")
 519              (list (calendar-gregorian-from-absolute (+ abs-p 3))
 520                    "Hol Hamoed Passover (second day)")
 521              (list (calendar-gregorian-from-absolute (+ abs-p 4))
 522                    "Hol Hamoed Passover (third day)")
 523              (list (calendar-gregorian-from-absolute (+ abs-p 5))
 524                    "Hol Hamoed Passover (fourth day)")
 525              (list (calendar-gregorian-from-absolute (+ abs-p 6))
 526                    "Passover (seventh day)")
 527              (list (calendar-gregorian-from-absolute (+ abs-p 7))
 528                    "Passover (eighth day)")
 529              (list (calendar-gregorian-from-absolute (+ abs-p 12))
 530                    "Yom HaShoah")
 531              (list (calendar-gregorian-from-absolute
 532                     (if (zerop (% abs-p 7))
 533                         (+ abs-p 18)
 534                       (if (= (% abs-p 7) 6)
 535                           (+ abs-p 19)
 536                         (+ abs-p 20))))
 537                    "Yom HaAtzma'ut")
 538              (list (calendar-gregorian-from-absolute (+ abs-p 33))
 539                    "Lag BaOmer")
 540              (list (calendar-gregorian-from-absolute (+ abs-p 43))
 541                    "Yom Yerushalim")
 542              (list (calendar-gregorian-from-absolute (+ abs-p 49))
 543                    "Erev Shavuot")
 544              (list (calendar-gregorian-from-absolute (+ abs-p 51))
 545                    "Shavuot (second day)")))
 546            (output-list
 547              (filter-visible-calendar-holidays mandatory)))
 548       (if all-hebrew-calendar-holidays
 549           (setq output-list
 550                 (append
 551                  (filter-visible-calendar-holidays optional)
 552                  output-list)))
 553       output-list)))
 554
 555 (defun calendar-holiday-function-tisha-b-av-etc ()
 556   "List of dates around Tisha B'Av, as visible in calendar window."
 557   (if (or (< displayed-month 5)
 558           (> displayed-month 9))
 559       nil;; None of the dates is visible
 560     (let* ((abs-t-a (calendar-absolute-from-hebrew
 561                       (list 5 9 (+ displayed-year 3760)))))
 562
 563       (filter-visible-calendar-holidays
 564        (list
 565         (list (calendar-gregorian-from-absolute
 566                (if (= (% abs-t-a 7) 6) (- abs-t-a 20) (- abs-t-a 21)))
 567               "Tzom Tammuz")
 568         (list (calendar-gregorian-from-absolute
 569                (calendar-dayname-on-or-before 6 abs-t-a))
 570               "Shabbat Hazon")
 571         (list (calendar-gregorian-from-absolute
 572                (if (= (% abs-t-a 7) 6) (1+ abs-t-a) abs-t-a))
 573               "Tisha B'Av")
 574         (list (calendar-gregorian-from-absolute
 575                (calendar-dayname-on-or-before 6 (+ abs-t-a 7)))
 576               "Shabbat Nahamu"))))))
 577
 578 (defun filter-visible-calendar-holidays (l)
 579   "Return a list of all visible holidays of those on L."
 580   (let ((visible)
 581         (p l))
 582     (while p
 583       (if (calendar-date-is-visible-p (car (car p)))
 584           (setq visible (append (list (car p)) visible)))
 585       (setq p (cdr p)))
 586     visible))
 587
 588 (provide 'holidays)
 589
 590 ;;; holidays.el ends here