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+;; Calendar functions.
+;; Copyright (C) 1988, 1989, 1990, 1991 Free Software Foundation, Inc.
+
+;; This file is part of GNU Emacs.
+
+;; GNU Emacs is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY.  No author or distributor
+;; accepts responsibility to anyone for the consequences of using it
+;; or for whether it serves any particular purpose or works at all,
+;; unless he says so in writing.  Refer to the GNU Emacs General Public
+;; License for full details.
+
+;; Everyone is granted permission to copy, modify and redistribute
+;; GNU Emacs, but only under the conditions described in the
+;; GNU Emacs General Public License.   A copy of this license is
+;; supposed to have been given to you along with GNU Emacs so you
+;; can know your rights and responsibilities.  It should be in a
+;; file named COPYING.  Among other things, the copyright notice
+;; and this notice must be preserved on all copies.
+
+;; This collection of functions implements a calendar window.  It generates
+;; generates a calendar for the current month, together with the previous and
+;; coming months, or for any other three-month period.  The calendar can be
+;; scrolled forward and backward in the window to show months in the past or
+;; future; the cursor can move forward and backward by days, weeks, or months,
+;; making it possible, for instance, to jump to the date a specified number of
+;; days, weeks, or months from the date under the cursor.  The user can
+;; display a list of holidays and other notable days for the period shown; the
+;; notable days can be marked on the calendar, if desired.  The user can also
+;; specify that dates having corresponding diary entries (in a file that the
+;; user specifies) be marked; the diary entries for any date can be viewed in
+;; a separate window.  The diary and the notable days can be viewed
+;; independently of the calendar.  Dates can be translated from the (usual)
+;; Gregorian calendar to the day of the year/days remaining in year, to the
+;; ISO commercial calendar, to the Julian (old style) calendar, to the Hebrew
+;; calendar, to the Islamic calendar, and to the French Revolutionary calendar.
+
+;; The diary related functions are in diary.el; the holiday related functions
+;; are in holiday.el
+
+;; Comments, corrections, and improvements should be sent to
+;;  Edward M. Reingold               Department of Computer Science
+;;  (217) 333-6733                   University of Illinois at Urbana-Champaign
+;;  reingold@cs.uiuc.edu             1304 West Springfield Avenue
+;;                                   Urbana, Illinois 61801
+
+;; GNU Emacs users too numerous to list pointed out a variety of problems
+;; with earlier forms of the `infinite' sliding calendar and suggested some
+;; of the features included in this package.  Especially significant in this
+;; regard was the suggestion of mark-diary-entries and view-diary-entries,
+;; together ideas for their implementation, by
+;;  Michael S. Littman               Cognitive Science Research Group
+;;  (201) 829-5155                   Bell Communications Research
+;;  mlittman@wind.bellcore.com       445 South St. Box 1961 (2L-331)
+;;                                   Morristown, NJ  07960
+
+;; The algorithms for the Hebrew calendar are those of the Rambam (Rabbi Moses
+;; Maimonides), from his Mishneh Torah, as implemented by
+;;  Nachum Dershowitz                Department of Computer Science
+;;  (217) 333-4219                   University of Illinois at Urbana-Champaign
+;;  nachum@cs.uiuc.edu               1304 West Springfield Avenue
+;;                                   Urbana, Illinois 61801
+
+;; Technical details of all the calendrical calculations can be found in
+;; ``Calendrical Calculations'' by Nachum Dershowitz and Edward M. Reingold,
+;; Software--Practice and Experience, Volume 20, Number 9 (September, 1990),
+;; pages 899-928.
+
+(defconst calendar-version "Version 4.01, released August 20, 1991")
+
+(defvar view-diary-entries-initially nil
+  "*If T, the diary entries for the current date will be displayed on entry.
+The diary is displayed in another window when the calendar is first displayed,
+if the current date is visible.  The number of days of diary entries displayed
+is governed by the variable `number-of-diary-entries'.")
+
+(defvar number-of-diary-entries 1
+  "*Specifies how many days of diary entries are to be displayed initially.
+This variable affects the diary display when the command M-x diary is used,
+or if the value of the variable `view-diary-entries-initially' is t.  For
+example, if the default value 1 is used, then only the current day's diary
+entries will be displayed.  If the value 2 is used, then both the current
+day's and the next day's entries will be displayed.  The value can also be
+a vector such as [0 2 2 2 2 4 1]; this value will cause no diary entries to
+be displayed on Sunday, the current date's and the next day's diary entries
+to be displayed Monday through Thursday, Friday through Monday's entries to
+be displayed on Friday, and only Saturday's entries to be displayed on
+Saturday.  This variable does not affect the diary display with the `d'
+command from the calendar; in that case, the prefix argument controls the
+number of days of diary entries displayed.")
+
+(defvar mark-diary-entries-in-calendar nil
+  "*If t, dates with diary entries will be marked in the calendar window.
+The marking symbol is specified by the variable `diary-entry-marker'.")
+
+(defvar diary-entry-marker "+"
+  "*The symbol used to mark dates that have diary entries.")
+
+(defvar view-calendar-holidays-initially nil
+  "*If t, the holidays for the current three month period will be displayed
+on entry.  The holidays are displayed in another window when the calendar is
+first displayed.")
+
+(defvar mark-holidays-in-calendar nil
+  "*If t, dates of holidays will be marked in the calendar window.
+The marking symbol is specified by the variable `calendar-holiday-marker'.")
+
+(defvar calendar-holiday-marker "*"
+  "*The symbol used to mark notable dates in the calendar.")
+
+(defvar all-hebrew-calendar-holidays nil
+  "*If nil, the holidays from the Hebrew calendar that are shown will
+include only those days of such major interest as to appear on secular
+calendars.  If t, the holidays shown in the calendar will include all
+special days that would be shown on a complete Hebrew calendar.")
+
+(defvar all-christian-calendar-holidays nil
+  "*If nil, the holidays from the Christian calendar that are shown will
+include only those days of such major interest as to appear on secular
+calendars.  If t, the holidays shown in the calendar will include all
+special days that would be shown on a complete Christian calendar.")
+
+(defvar all-islamic-calendar-holidays nil
+  "*If nil, the holidays from the Islamic calendar that are shown will
+include only those days of such major interest as to appear on secular
+calendars.  If t, the holidays shown in the calendar will include all
+special days that would be shown on a complete Islamic calendar.")
+
+(defvar initial-calendar-window-hook nil
+  "*List of functions to be called when the calendar window is first opened.
+The functions invoked are called after the calendar window is opened, but
+once opened is never called again.  Leaving the calendar with the `q' command
+and reentering it will cause these functions to be called again.")
+
+(defvar today-visible-calendar-hook nil
+  "*List of functions called whenever the current date is visible.
+This can be used, for example, to replace today's date with asterisks; a
+function `calendar-star-date' is included for this purpose:
+    (setq today-visible-calendar-hook 'calendar-star-date)
+It could also be used to mark the current date with `='; a function is also
+provided for this:
+    (setq today-visible-calendar-hook 'calendar-mark-today)
+
+The corresponding variable `today-invisible-calendar-hook' is the list of
+functions called when the calendar function was called when the current
+date is not visible in the window.
+
+Other than the use of the provided functions, the changing of any
+characters in the calendar buffer by the hooks may cause the failure of the
+functions that move by days and weeks.")
+
+(defvar today-invisible-calendar-hook nil
+  "*List of functions called whenever the current date is not visible.
+
+The corresponding variable `today-visible-calendar-hook' is the list of
+functions called when the calendar function was called when the current
+date is visible in the window.
+
+Other than the use of the provided functions, the changing of any
+characters in the calendar buffer by the hooks may cause the failure of the
+functions that move by days and weeks.")
+
+(defvar diary-file "~/diary"
+  "*Name of the file in which one's personal diary of dates is kept.
+
+The file's entries are lines in any of the forms
+
+            MONTH/DAY
+            MONTH/DAY/YEAR
+            MONTHNAME DAY
+            MONTHNAME DAY, YEAR
+            DAYNAME
+
+at the beginning of the line; the remainder of the line is the diary entry
+string for that date.  MONTH and DAY are one or two digit numbers, YEAR is
+a number and may be written in full or abbreviated to the final two digits.
+If the date does not contain a year, it is generic and applies to any year.
+DAYNAME entries apply to any date on which is on that day of the week.
+MONTHNAME and DAYNAME can be spelled in full, abbreviated to three
+characters (with or without a period), capitalized or not.  Any of DAY,
+MONTH, or MONTHNAME, YEAR can be `*' which matches any day, month, or year,
+respectively.
+
+The European style (in which the day precedes the month) can be used
+instead, if you execute `european-calendar' when in the calendar, or set
+`european-calendar-style' to t in your .emacs file.  The European forms are
+
+            DAY/MONTH
+            DAY/MONTH/YEAR
+            DAY MONTHNAME
+            DAY MONTHNAME YEAR
+            DAYNAME
+
+To revert to the default American style from the European style, execute
+`american-calendar' in the calendar.
+
+A diary entry can be preceded by a diary-nonmarking-symbol (ordinarily `&')
+to make that entry nonmarking--that is, it will not be marked on dates in
+the calendar window but will appear in a diary window.
+
+Multiline diary entries are made by indenting lines after the first with
+either a TAB or one or more spaces.
+
+Lines not in one the above formats are ignored.  Here are some sample diary
+entries (in the default American style):
+
+     12/22/1988 Twentieth wedding anniversary!!
+     &1/1. Happy New Year!
+     10/22 Ruth's birthday.
+     21: Payday
+     Tuesday--weekly meeting with grad students at 10am
+              Supowit, Shen, Bitner, and Kapoor to attend.
+     1/13/89 Friday the thirteenth!!
+     &thu 4pm squash game with Lloyd.
+     mar 16 Dad's birthday
+     April 15, 1989 Income tax due.
+     &* 15 time cards due.
+
+If the first line of a diary entry consists only of the date or day name with
+no trailing blanks or punctuation, then that line will not be displayed in the
+diary window; only the continuation lines will be shown.  For example, the
+single diary entry
+
+     02/11/1989
+      Bill Blattner visits Princeton today
+      2pm Cognitive Studies Committee meeting
+      2:30-5:30 Lizzie at Lawrenceville for `Group Initiative'
+      4:00pm Jamie Tappenden
+      7:30pm Dinner at George and Ed's for Alan Ryan
+      7:30-10:00pm dance at Stewart Country Day School
+
+will appear in the diary window without the date line at the beginning.  This
+facility allows the diary window to look neater, but can cause confusion if
+used with more than one day's entries displayed.
+
+Diary entries can be based on Lisp sexps.  For example, the diary entry
+
+      %%(diary-block 11 1 1990 11 10 1990) Vacation
+
+causes the diary entry \"Vacation\" to appear from November 1 through November
+10, 1990.  Other functions available are `diary-float', `diary-anniversary',
+`diary-cyclic', `day-of-year', `iso-date', `commercial-date', `french-date',
+`hebrew-date', `islamic-date', `parasha', `omer', and `rosh-hodesh'.  See the
+documentation for the function `list-sexp-diary-entries' for more details.
+
+Diary entries based on the Hebrew and/or the Islamic calendar are also
+possible, but because these are somewhat slow, they are ignored
+unless you set the `nongregorian-diary-listing-hook' and the
+`nongregorian-diary-marking-hook' appropriately.  See the documentation
+for these functions for details.
+
+Diary files can contain directives to include the contents of other files; for
+details, see the documentation for the variable `list-diary-entries-hook'.")
+
+(defvar diary-nonmarking-symbol "&"
+  "*The symbol used to indicate that a diary entry is not to be marked in the
+calendar window.")
+
+(defvar hebrew-diary-entry-symbol "H"
+  "*The symbol used to indicate that a diary entry is according to the
+Hebrew calendar.")
+
+(defvar islamic-diary-entry-symbol "I"
+  "*The symbol used to indicate that a diary entry is according to the
+Islamic calendar.")
+
+(defvar diary-include-string "#include"
+  "*The string used to indicate the inclusion of another file of diary entries
+in diary-file.  See the documentation for the function
+`include-other-diary-files'.")
+
+(defvar sexp-diary-entry-symbol "%%"
+  "*The string used to indicate a sexp diary entry in diary-file.
+See the documentation for the function `list-sexp-diary-entries'.")
+
+(defvar abbreviated-calendar-year t
+  "*Interpret a two-digit year DD in a diary entry as being either 19DD or
+20DD, as appropriate, for the Gregorian calendar; similarly for the Hebrew and
+Islamic calendars.  If this variable is nil, years must be written in full.")
+
+(defvar european-calendar-style nil
+  "*Use the European style of dates in the diary and in any displays.  If this
+variable is t, a date 1/2/1990 would be interpreted as February 1, 1990.
+The accepted European date styles are
+
+            DAY/MONTH
+            DAY/MONTH/YEAR
+            DAY MONTHNAME
+            DAY MONTHNAME YEAR
+            DAYNAME
+
+Names can be capitalized or not, written in full, or abbreviated to three
+characters with or without a period.")
+
+(defvar american-date-diary-pattern
+  '((month "/" day "[^/0-9]")
+    (month "/" day "/" year "[^0-9]")
+    (monthname " *" day "[^,0-9]")
+    (monthname " *" day ", *" year "[^0-9]")
+    (dayname "\\W"))
+  "*List of pseudo-patterns describing the American patterns of date used.
+See the documentation of diary-date-forms for an explanantion.")
+
+(defvar european-date-diary-pattern
+  '((day "/" month "[^/0-9]")
+    (day "/" month "/" year "[^0-9]")
+    (backup day " *" monthname "\\W+\\<[^*0-9]")
+    (day " *" monthname " *" year "[^0-9]")
+    (dayname "\\W"))
+  "*List of pseudo-patterns describing the European patterns of date used.
+See the documentation of diary-date-forms for an explanantion.")
+
+(defvar diary-date-forms
+  (if european-calendar-style
+      european-date-diary-pattern
+    american-date-diary-pattern)
+  "*List of pseudo-patterns describing the forms of date used in the diary.
+The patterns on the list must be MUTUALLY EXCLUSIVE and must should not match
+any portion of the diary entry itself, just the date component.
+
+A pseudo-pattern is a list of regular expressions and the keywords `month',
+`day', `year', `monthname', and `dayname'.  The keyword `monthname' will
+match the name of the month, capitalized or not, or its three-letter
+abbreviation, followed by a period or not; it will also match `*'.
+Similarly, `dayname' will match the name of the day, capitalized or not, or
+its three-letter abbreviation, followed by a period or not.  The keywords
+`month', `day', and `year' will match those numerical values, preceded by
+arbitrarily many zeros; they will also match `*'.
+
+The matching of the diary entries with the date forms is done with the
+standard syntax table from Fundamental mode, but with the `*' changed so
+that it is a word constituent.
+
+If, to be mutually exclusive, a pseudo-pattern must match a portion of the
+diary entry itself, the first element of the pattern MUST be `backup'.  This
+directive causes the the date recognizer to back up to the beginning of the
+current word of the diary entry, so in no case can the pattern match more
+than a portion of the first word of the diary entry.")
+
+(defvar european-calendar-display-form
+  '(dayname ", " day " " monthname " " year)
+  "*The pseudo-pattern that governs the way a Gregorian date is formatted
+in the European style.  See the documentation of calendar-date-display-forms
+for an explanantion.")
+
+(defvar american-calendar-display-form
+  '(dayname ", " monthname " " day ", " year)
+  "*The pseudo-pattern that governs the way a Gregorian date is formatted
+in the American style.  See the documentation of calendar-date-display-forms
+for an explanantion.")
+
+(defvar calendar-date-display-form
+  (if european-calendar-style
+      european-calendar-display-form
+    american-calendar-display-form)
+  "*The pseudo-pattern that governs the way a Gregorian date is formatted
+as a string by the function `calendar-date-string'.  A pseudo-pattern is a
+list of expressions that can involve the keywords `month', `day', and
+`year', all numbers in string form, and `monthname' and `dayname', both
+alphabetic strings.  For example, the ISO standard would use the pseudo-
+pattern
+
+       '(year \"-\" month \"-\" day)
+
+while a typical American form would be
+
+       '(month \"/\" day \"/\" (substring year -2))
+
+and
+
+       '((format \"%9s, %9s %2s, %4s\" dayname monthname day year))
+
+would give the usual American style in fixed-length fields.
+
+See the documentation of the function `calendar-date-string'.")
+
+(defun european-calendar ()
+  "Set the interpretation and display of dates to the European style."
+  (interactive)
+  (setq european-calendar-style t)
+  (setq calendar-date-display-form european-calendar-display-form)
+  (setq diary-date-forms european-date-diary-pattern)
+  (update-calendar-mode-line))
+
+(defun american-calendar ()
+  "Set the interpretation and display of dates to the American style."
+  (interactive)
+  (setq european-calendar-style nil)
+  (setq calendar-date-display-form american-calendar-display-form)
+  (setq diary-date-forms american-date-diary-pattern)
+  (update-calendar-mode-line))
+
+(defvar print-diary-entries-hook
+  '(add-diary-heading lpr-buffer (lambda nil (kill-buffer temp-buffer)))
+  "*List of functions to be called after a temporary buffer is prepared
+with the diary entries currently visible in the diary buffer.  The default
+value adds a heading (formed from the information in the mode line of the
+diary buffer), does the printing, and kills the buffer.  Other uses might
+include, for example, rearranging the lines into order by day and time,
+saving the buffer instead of deleting it, or changing the function used to
+do the printing.")
+
+(defvar list-diary-entries-hook nil
+  "*List of functions to be called after the diary file is culled for
+relevant entries. It is to be used for diary entries that are not found in
+the diary file.
+
+A function `include-other-diary-files' is provided for use as the value of
+this hook.  This function enables you to use shared diary files together
+with your own.  The files included are specified in the diary-file by lines
+of the form
+
+        #include \"filename\"
+
+This is recursive; that is, #include directives in files thus included are
+obeyed.  You can change the \"#include\" to some other string by changing
+the variable `diary-include-string'.  When you use `include-other-diary-files'
+as part of the list-diary-entries-hook, you will probably also want to use the
+function `mark-included-diary-files' as part of the mark-diary-entries-hook.
+
+For example, you could use
+
+     (setq list-diary-entries-hook
+           '(include-other-diary-files
+             (lambda nil
+                     (setq diary-entries-list
+                           (sort diary-entries-list 'diary-entry-compare)))))
+     (setq diary-display-hook 'fancy-diary-display)
+
+in your .emacs file to cause the fancy diary buffer to be displayed with
+diary entries from various included files, each day's entries sorted into
+lexicographic order.")
+
+(defvar diary-display-hook 'simple-diary-display
+  "*List of functions that handle the display of the diary.
+
+Ordinarily, this just displays the diary buffer (with holidays indicated in
+the mode line), if there are any relevant entries.  At the time these
+functions are called, the variable `diary-entries-list' is a list, in order
+by date, of all relevant diary entries in the form of ((MONTH DAY YEAR)
+STRING), where string is the diary entry for the given date.  This can be
+used, for example, to handle appointment notification, prepare a different
+buffer for display (perhaps combined with holidays), or produce hard copy
+output.
+
+A function `fancy-diary-display' is provided as an alternative
+choice for this hook; this function prepares a special noneditable diary
+buffer with the relevant diary entries that has neat day-by-day arrangement
+with headings.  The fancy diary buffer will show the holidays unless the
+variable `holidays-in-diary-buffer' is set to nil.  Ordinarily, the fancy
+diary buffer will not show days for which there are no diary entries, even
+if that day is a holiday; if you want such days to be shown in the fancy
+diary buffer, set the variable `diary-list-include-blanks' to t.")
+
+(defvar nongregorian-diary-listing-hook nil
+  "*List of functions to be called for the diary file and included files as
+they are processed for listing diary entries.  You can use any or all of
+`list-hebrew-diary-entries', `yahrzeit-diary-entry', and
+`list-islamic-diary-entries'.  The documentation for these functions
+describes the style of such diary entries.")
+
+(defvar mark-diary-entries-hook nil
+  "*List of functions called after marking diary entries in the calendar.
+
+A function `mark-included-diary-files' is also provided for use as the
+mark-diary-entries-hook; it enables you to use shared diary files together
+with your own.  The files included are specified in the diary-file by lines
+of the form
+        #include \"filename\"
+This is recursive; that is, #include directives in files thus included are
+obeyed.  You can change the \"#include\" to some other string by changing the
+variable `diary-include-string'.  When you use `mark-included-diary-files' as
+part of the mark-diary-entries-hook, you will probably also want to use the
+function `include-other-diary-files' as part of the list-diary-entries-hook.")
+
+(defvar nongregorian-diary-marking-hook nil
+  "*List of functions to be called as the diary file and included files are
+processed for marking diary entries.  You can use either or both of
+mark-hebrew-diary-entries and mark-islamic-diary-entries.  The documentation
+for these functions describes the style of such diary entries.")
+
+(defvar diary-list-include-blanks nil
+  "*If nil, do not include days with no diary entry in the list of diary
+entries.  Such days will then not be shown in the the fancy diary buffer,
+even if they are holidays.")
+
+(defvar holidays-in-diary-buffer t
+  "*If t, the holidays will be indicated in the mode line of the diary buffer
+(or in the fancy diary buffer next to the date).  This slows down the diary
+functions somewhat; setting it to nil will make the diary display faster.")
+
+(defvar calendar-holidays
+  '(
+;;  General Holidays (American)
+    (fixed 1 1 "New Year's Day")
+    (float 1 1 3 "Martin Luther King Day")
+    (fixed 2 2 "Ground Hog Day")
+    (fixed 2 14 "Valentine's Day")
+    (float 2 1 3 "President's Day")
+    (fixed 3 17 "St. Patrick's Day")
+    (fixed 4 1 "April Fool's Day")
+    (float 4 0 1 "Daylight Savings Time Begins")
+    (float 5 0 2 "Mother's Day")
+    (float 5 1 -1 "Memorial Day")
+    (fixed 6 14 "Flag Day")
+    (float 6 0 3 "Father's Day")
+    (fixed 7 4 "Independence Day")
+    (float 9 1 1 "Labor Day")
+    (float 10 1 2 "Columbus Day")
+    (float 10 0 -1 "Daylight Savings Time Ends")
+    (fixed 10 31 "Halloween")
+    (fixed 11 11 "Veteran's Day")
+    (float 11 4 4 "Thanksgiving")
+
+;;  Christian Holidays
+    (if all-christian-calendar-holidays
+        (fixed 1 6 "Epiphany"))
+    (easter-etc)
+    (if all-christian-calendar-holidays
+        (fixed 8 15 "Assumption"))
+    (if all-christian-calendar-holidays
+        (advent))
+    (fixed 12 25 "Christmas")
+    (if all-christian-calendar-holidays
+        (julian 12 25 "Eastern Orthodox Christmas"))
+
+;;  Jewish Holidays
+    (rosh-hashanah-etc)
+    (if all-hebrew-calendar-holidays
+        (julian 11
+                (let* ((m displayed-month)
+                       (y displayed-year)
+                       (year))
+                  (increment-calendar-month m y -1)
+                  (let ((year (extract-calendar-year
+                               (calendar-julian-from-absolute
+                                (calendar-absolute-from-gregorian
+                                 (list m 1 y))))))
+                    (if (zerop (% (1+ year) 4))
+                        22
+                      21))) "\"Tal Umatar\" (evening)"))
+    (if all-hebrew-calendar-holidays
+        (hanukkah)
+      (hebrew 9 25 "Hanukkah"))
+    (if all-hebrew-calendar-holidays
+      (hebrew 10
+              (let ((h-year (extract-calendar-year
+                             (calendar-hebrew-from-absolute
+                              (calendar-absolute-from-gregorian
+                               (list displayed-month 28 displayed-year))))))
+                (if (= (% (calendar-absolute-from-hebrew (list 10 10 h-year))
+                        7)
+                       6)
+                    11 10))
+              "Tzom Teveth"))
+    (if all-hebrew-calendar-holidays
+        (hebrew 11 15 "Tu B'Shevat"))
+    (if all-hebrew-calendar-holidays
+        (hebrew
+         11
+         (let ((m displayed-month)
+               (y displayed-year))
+           (increment-calendar-month m y 1)
+           (let* ((h-year (extract-calendar-year
+                           (calendar-hebrew-from-absolute
+                            (calendar-absolute-from-gregorian
+                             (list m
+                                   (calendar-last-day-of-month m y)
+                                   y)))))
+                  (s-s
+                   (calendar-hebrew-from-absolute
+                    (if (=
+                         (% (calendar-absolute-from-hebrew
+                             (list 7 1 h-year))
+                            7)
+                         6)
+                        (calendar-dayname-on-or-before
+                         6 (calendar-absolute-from-hebrew
+                            (list 11 17 h-year)))
+                      (calendar-dayname-on-or-before
+                       6 (calendar-absolute-from-hebrew
+                          (list 11 16 h-year))))))
+                  (day (extract-calendar-day s-s)))
+             day))
+         "Shabbat Shirah"))
+    (passover-etc)
+    (if (and all-hebrew-calendar-holidays
+             (let* ((m displayed-month)
+                    (y displayed-year)
+                    (year))
+               (increment-calendar-month m y -1)
+               (let ((year (extract-calendar-year
+                            (calendar-julian-from-absolute
+                             (calendar-absolute-from-gregorian
+                              (list m 1 y))))))
+                 (= 21 (% year 28)))))
+        (julian 3 26 "Kiddush HaHamah"))
+    (if all-hebrew-calendar-holidays
+        (tisha-b-av-etc))
+
+;;  Islamic Holidays
+    (islamic 1 1 (format "Islamic New Year %d"
+                         (let ((m displayed-month)
+                               (y displayed-year))
+                           (increment-calendar-month m y 1)
+                           (extract-calendar-year
+                            (calendar-islamic-from-absolute
+                             (calendar-absolute-from-gregorian
+                              (list m (calendar-last-day-of-month m y) y)))))))
+    (if all-islamic-calendar-holidays
+        (islamic 1 10 "Ashura"))
+    (if all-islamic-calendar-holidays
+        (islamic 3 12 "Mulad-al-Nabi"))
+    (if all-islamic-calendar-holidays
+        (islamic 7 26 "Shab-e-Mi'raj"))
+    (if all-islamic-calendar-holidays
+        (islamic 8 15 "Shab-e-Bara't"))
+    (islamic 9 1 "Ramadan Begins")
+    (if all-islamic-calendar-holidays
+        (islamic 9 27 "Shab-e Qadr"))
+    (if all-islamic-calendar-holidays
+        (islamic 10 1 "Id-al-Fitr"))
+    (if all-islamic-calendar-holidays
+        (islamic 12 10 "Id-al-Adha")))
+  "List of notable days for the command M-x holidays.
+Additional holidays are easy to add to the list.  The possible holiday-forms
+are as follows:
+
+    (fixed MONTH DAY STRING)   a fixed date on the Gregorian calendar
+    (float MONTH DAYNAME K STRING) the Kth DAYNAME in MONTH on the Gregorian
+                               calendar (0 for Sunday, etc.); K<0 means
+                               count back from the end of the month
+    (hebrew MONTH DAY STRING)  a fixed date on the Hebrew calendar
+    (islamic MONTH DAY STRING) a fixed date on the Islamic calendar
+    (julian MONTH DAY STRING)  a fixed date on the Julian calendar
+    (if BOOLEAN HOLIDAY-FORM &optional HOLIDAY-FORM) gives a choice between
+                               two holidays based on the value of BOOLEAN
+    (FUNCTION &optional ARGS)  dates requiring special computation; ARGS,
+                               if any, are passed in a list to the function
+                               `calendar-holiday-function-FUNCTION'
+
+For example, to add Bastille Day, celebrated in France on July 14, add
+
+     (fixed 7 14 \"Bastille Day\")
+
+to the list.  To add Hurricane Supplication Day, celebrated in the Virgin
+Islands on the fourth Monday in August, add
+
+     (float 8 1 4 \"Hurricane Supplication Day\")
+
+to the list (the last Monday would be specified with `-1' instead of `4').
+To add the last day of Hanukah to the list, use
+
+     (hebrew 10 2 \"Last day of Hanukah\")
+
+since the Hebrew months are numbered with 1 starting from Nisan, while to
+add the Islamic feast celebrating Mohammed's birthday use
+
+     (islamic 3 12 \"Mohammed's Birthday\")
+
+since the Islamic months are numbered from 1 starting with Muharram.  To
+add Thomas Jefferson's birthday, April 2, 1743 (Julian), use
+
+     (julian 4 2 \"Jefferson's Birthday\")
+
+To include a holiday conditionally, use the if form.  For example, to
+include American presidential elections, which occur on the first Tuesday
+after the first Monday in November of years divisble by 4, add
+
+     (if (zerop (% displayed-year 4))
+         (fixed 11
+                (extract-calendar-day
+                 (calendar-gregorian-from-absolute
+                  (1+ (calendar-dayname-on-or-before
+                       1 (+ 6 (calendar-absolute-from-gregorian
+                               (list 11 1 displayed-year)))))))
+                \"US Presidential Election\"))
+
+to the list.  To include the phases of the moon, add
+
+     (lunar-phases)
+
+to the holiday list, where `calendar-holiday-function-lunar-phases' is an
+Emacs-Lisp function that you've written to return a (possibly empty) list of
+the relevant VISIBLE dates with descriptive strings such as
+
+     (((2 6 1989) \"New Moon\") ((2 12 1989) \"First Quarter Moon\") ... )
+
+The fixed, float, hebrew, islamic, julian and if forms are implemented by
+the inclusion of the functions `calendar-holiday-function-fixed',
+`calendar-holiday-function-float', `calendar-holiday-function-hebrew',
+`calendar-holiday-function-islamic', `calendar-holiday-function-julian',
+and `calendar-holiday-function-if', respectively.")
+
+
+(defconst calendar-buffer "*Calendar*"
+  "Name of the buffer used for the calendar.")
+
+(defconst holiday-buffer "*Holidays*"
+  "Name of the buffer used for the displaying the holidays.")
+
+(defconst fancy-diary-buffer "*Fancy Diary Entries*"
+  "Name of the buffer used for the optional fancy display of the diary.")
+
+(defmacro increment-calendar-month (mon yr n)
+  "Move the variables MON and YR to the month and year N months forward
+if N is positive or backward if N is negative."
+  (` (let (( macro-y (+ (* (, yr) 12) (, mon) -1 (, n) )))
+       (setq (, mon) (1+ (% macro-y 12) ))
+       (setq (, yr) (/ macro-y 12)))))
+
+(defmacro calendar-for-loop (var from init to final do &rest body)
+  "Execute a for loop."
+  (` (let (( (, var) (1- (, init)) ))
+       (while (>= (, final) (setq (, var) (1+ (, var))))
+         (,@ body)))))
+
+(defmacro calendar-sum (index initial condition expression)
+  "For INDEX = INITIAL and successive integers, as long as CONDITION holds,
+sum EXPRESSION."
+  (` (let (( (, index) (, initial))
+             (sum 0))
+       (while (, condition)
+         (setq sum (+ sum (, expression) ))
+         (setq (, index) (1+ (, index))))
+       sum)))
+
+(defmacro extract-calendar-month (date)
+  "Extract the month part of DATE which has the form (month day year)."
+  (` (car (, date))))
+
+(defmacro extract-calendar-day (date)
+  "Extract the day part of DATE which has the form (month day year)."
+  (` (car (cdr (, date)))))
+
+(defmacro extract-calendar-year (date)
+  "Extract the year part of DATE which has the form (month day year)."
+  (` (car (cdr (cdr (, date))))))
+
+(defun calendar (&optional arg)
+  "Display a three-month calendar in another window.
+The three months appear side by side, with the current month in the middle
+surrounded by the previous and next months.  The cursor is put on today's date.
+
+This function is suitable for execution in a .emacs file; appropriate setting
+of the variable `view-diary-entries-initially' will cause the diary entries for
+the current date to be displayed in another window.  The value of the variable
+`number-of-diary-entries' controls the number of days of diary entries
+displayed upon initial display of the calendar.
+
+An optional prefix argument ARG causes the calendar displayed to be ARG
+months in the future if ARG is positive or in the past if ARG is negative;
+in this case the cursor goes on the first day of the month.
+
+Once in the calendar window, future or past months can be moved into view.
+Arbitrary months can be displayed, or the calendar can be scrolled forward
+or backward.
+
+The cursor can be moved forward or backward by one day, one week, one month,
+or one year.  All of these commands take prefix arguments which, when negative,
+cause movement in the opposite direction.  For convenience, the digit keys
+and the minus sign are automatically prefixes.  The window is replotted as
+necessary to display the desired date.
+
+Diary entries can be marked on the calendar or displayed in another window.
+
+Use M-x describe-mode for details of the key bindings in the calendar window.
+
+The Gregorian calendar is assumed.
+
+After preparing the calendar window initially, the hooks given by the variable
+`initial-calendar-window-hook' are run.
+
+The hooks given by the variable `today-visible-calendar-hook' are run
+everytime the calendar window gets scrolled, if the current date is visible
+in the window.  If it is not visible, the hooks given by the variable
+`today-invisible-calendar-hook' are run.  Thus, for example, setting
+`today-visible-calendar-hook' to 'calendar-star-date will cause today's date
+to be replaced by asterisks to highlight it whenever it is in the window."
+  (interactive "P")
+  (setq arg (if arg (prefix-numeric-value arg) 0))
+  (set-buffer (get-buffer-create calendar-buffer))
+  (calendar-mode)
+  (setq calendar-window-configuration (current-window-configuration))
+  (let ((pop-up-windows t)
+        (split-height-threshold 1000))
+    (pop-to-buffer calendar-buffer)
+    (regenerate-calendar-window arg)
+    (let ((date (list current-month current-day current-year)))
+      (if (and view-diary-entries-initially (calendar-date-is-visible-p date))
+          (view-diary-entries
+           (if (vectorp number-of-diary-entries)
+               (aref number-of-diary-entries (calendar-day-of-week date))
+             number-of-diary-entries))))
+    (let* ((diary-buffer (get-file-buffer diary-file))
+           (diary-window (if diary-buffer (get-buffer-window diary-buffer)))
+           (split-height-threshold (if diary-window 2 1000)))
+      (if view-calendar-holidays-initially
+          (list-calendar-holidays))))
+  (run-hooks 'initial-calendar-window-hook))
+
+(autoload 'view-diary-entries "diary"
+  "Prepare and display a buffer with diary entries.
+Searches the file diary-file for entries that match ARG days starting with
+the date indicated by the cursor position in the displayed three-month
+calendar."
+  t)
+
+(autoload 'show-all-diary-entries "diary"
+  "Show all of the diary entries in the diary-file.
+This function gets rid of the selective display of the diary-file so that
+all entries, not just some, are visible.  If there is no diary buffer, one
+is created."
+  t)
+
+(autoload 'mark-diary-entries "diary"
+  "Mark days in the calendar window that have diary entries.
+Each entry in diary-file visible in the calendar window is marked."
+  t)
+
+(autoload 'insert-diary-entry "diary"
+  "Insert a diary entry for the date indicated by point."
+  t)
+
+(autoload 'insert-weekly-diary-entry "diary"
+  "Insert a weekly diary entry for the day of the week indicated by point."
+  t)
+
+(autoload 'insert-monthly-diary-entry "diary"
+  "Insert a monthly diary entry for the day of the month indicated by point."
+  t)
+
+(autoload 'insert-yearly-diary-entry "diary"
+  "Insert an annual diary entry for the day of the year indicated by point."
+  t)
+
+(autoload 'insert-anniversary-diary-entry "diary"
+  "Insert an anniversary diary entry for the date indicated by point."
+  t)
+
+(autoload 'insert-block-diary-entry "diary"
+  "Insert a block diary entry for the dates indicated by point and mark."
+  t)
+
+(autoload 'insert-cyclic-diary-entry "diary"
+  "Insert a cyclic diary entry starting at the date indicated by point."
+  t)
+
+(autoload 'insert-hebrew-diary-entry "diary"
+  "Insert a diary entry for the Hebrew date corresponding to the date
+indicated by point."
+  t)
+
+(autoload 'insert-monthly-hebrew-diary-entry "diary"
+  "Insert a monthly diary entry for the day of the Hebrew month corresponding
+to the date indicated by point."
+  t)
+
+(autoload 'insert-yearly-hebrew-diary-entry "diary"
+  "Insert an annual diary entry for the day of the Hebrew year corresponding
+to the date indicated by point."
+  t)
+
+(autoload 'insert-islamic-diary-entry "diary"
+  "Insert a diary entry for the Islamic date corresponding to the date
+indicated by point."
+  t)
+
+(autoload 'insert-monthly-islamic-diary-entry "diary"
+  "Insert a monthly diary entry for the day of the Islamic month corresponding
+to the date indicated by point."
+  t)
+
+(autoload 'insert-yearly-islamic-diary-entry "diary"
+  "Insert an annual diary entry for the day of the Islamic year corresponding
+to the date indicated by point."
+  t)
+
+(autoload 'list-calendar-holidays "holidays"
+  "Create a buffer containing the holidays for the current calendar window.
+The holidays are those in the list `calendar-notable-days'.  Returns t if any
+holidays are found, nil if not."
+  t)
+
+(autoload 'mark-calendar-holidays "holidays"
+  "Mark notable days in the calendar window."
+  t)
+
+(autoload 'calendar-cursor-holidays "holidays"
+  "Find holidays for the date specified by the cursor in the calendar window."
+  t)
+
+(defun regenerate-calendar-window (&optional arg)
+  "Generate the calendar window, offset from the current date by ARG months."
+  (if (not arg) (setq arg 0))
+  (let* ((buffer-read-only nil)
+         (today-visible (and (<= arg 1) (>= arg -1)))
+         (today (calendar-current-date))
+         (month (extract-calendar-month today))
+         (day (extract-calendar-day today))
+         (year (extract-calendar-year today))
+         (day-in-week (calendar-day-of-week today)))
+    (update-calendar-mode-line)
+    (setq current-month month)
+    (setq current-day day)
+    (setq current-year year)
+    (increment-calendar-month month year arg)
+    (generate-calendar month year)
+    (calendar-cursor-to-visible-date
+     (if today-visible today (list displayed-month 1 displayed-year)))
+    (set-buffer-modified-p nil)
+    (or (one-window-p t)
+        (/= (screen-width) (window-width))
+        (shrink-window (- (window-height) 9)))
+    (sit-for 0)
+    (and mark-holidays-in-calendar
+         (mark-calendar-holidays)
+         (sit-for 0))
+    (unwind-protect
+        (if mark-diary-entries-in-calendar (mark-diary-entries))
+      (if today-visible
+          (run-hooks 'today-visible-calendar-hook)
+        (run-hooks 'today-invisible-calendar-hook)))))
+
+(defun generate-calendar (month year)
+  "Generate a three-month Gregorian calendar centered around MONTH, YEAR."
+  (if (< (+ month (* 12 (1- year))) 2)
+      (error "Months before February, 1 AD are not available."))
+  (setq displayed-month month)
+  (setq displayed-year year)
+  (erase-buffer)
+  (increment-calendar-month month year -1)
+  (calendar-for-loop i from 0 to 2 do
+       (generate-calendar-month month year (+ 5 (* 25 i)))
+       (increment-calendar-month month year 1)))
+
+(defun generate-calendar-month (month year indent)
+  "Produce a calendar for MONTH, YEAR on the Gregorian calendar.
+The calendar is inserted in the buffer starting at the line on which point
+is currently located, but indented INDENT spaces.  The indentation is done
+from the first character on the line and does not disturb the first INDENT
+characters on the line."
+  (let* ((first-day-of-month (calendar-day-of-week (list month 1 year)))
+         (first-saturday (- 7 first-day-of-month))
+         (last (calendar-last-day-of-month month year)))
+    (goto-char (point-min))
+    (calendar-insert-indented
+       (format "   %s %d" (calendar-month-name month) year) indent t)
+    (calendar-insert-indented " S  M Tu  W Th  F  S" indent t)
+    (calendar-insert-indented "" indent);; Move to appropriate spot on line
+    ;; Add blank days before the first of the month
+    (calendar-for-loop i from 1 to first-day-of-month do
+        (insert "   "))
+    ;; Put in the days of the month
+    (calendar-for-loop i from 1 to last do
+         (insert (format "%2d " i))
+         (and (= (% i 7) (% first-saturday 7))
+              (/= i last)
+              (calendar-insert-indented "" 0 t)    ;; Force onto following line
+              (calendar-insert-indented "" indent)))));; Go to proper spot
+
+(defun calendar-insert-indented (string indent &optional newline)
+  "Insert STRING at column INDENT.
+If the optional parameter NEWLINE is t, leave point at start of next line,
+inserting a newline if there was no next line; otherwise, leave point after
+the inserted text.  Value is always t."
+  ;; Try to move to that column.
+  (move-to-column indent)
+  ;; If line is too short, indent out to that column.
+  (if (< (current-column) indent)
+      (indent-to indent))
+  (insert string)
+  ;; Advance to next line, if requested.
+  (if newline
+      (progn
+        (end-of-line)
+        (if (eobp)
+            (newline)
+          (forward-line 1))))
+  t)
+
+(defun redraw-calendar ()
+  "Redraw the calendar display."
+  (interactive)
+  (let ((cursor-date (calendar-cursor-to-date)))
+    (regenerate-calendar-window
+     (calendar-interval current-month current-year
+                        displayed-month displayed-year))
+    (calendar-cursor-to-visible-date cursor-date)))
+
+(defvar calendar-mode-map nil)
+(if calendar-mode-map
+    nil
+  (setq calendar-mode-map (make-sparse-keymap))
+  (calendar-for-loop i from 0 to 9 do
+       (define-key calendar-mode-map (int-to-string i) 'digit-argument))
+  (let ((l (list 'narrow-to-region 'mark-word 'mark-sexp 'mark-paragraph
+                 'mark-defun 'mark-whole-buffer 'mark-page 'kill-region
+                 'copy-region-as-kill 'downcase-region 'upcase-region
+                 'capitalize-region 'write-region)))
+    (while (car l)
+      (let ((k (where-is-internal (car l))))
+        (while (car k)
+          (define-key calendar-mode-map (car k) 'calendar-not-implemented)
+          (setq k (cdr k)))
+        (setq l (cdr l)))))
+  (define-key calendar-mode-map "-"     'negative-argument)
+  (define-key calendar-mode-map "\C-x>" 'scroll-calendar-right)
+  (define-key calendar-mode-map "\ev"   'scroll-calendar-right-three-months)
+  (define-key calendar-mode-map "\C-x<" 'scroll-calendar-left)
+  (define-key calendar-mode-map "\C-v"  'scroll-calendar-left-three-months)
+  (define-key calendar-mode-map "\C-b"  'calendar-backward-day)
+  (define-key calendar-mode-map "\C-p"  'calendar-backward-week)
+  (define-key calendar-mode-map "\e["   'calendar-backward-month)
+  (define-key calendar-mode-map "\C-x[" 'calendar-backward-year)
+  (define-key calendar-mode-map "\C-f"  'calendar-forward-day)
+  (define-key calendar-mode-map "\C-n"  'calendar-forward-week)
+  (define-key calendar-mode-map "\e]"   'calendar-forward-month)
+  (define-key calendar-mode-map "\C-x]" 'calendar-forward-year)
+  (define-key calendar-mode-map "\C-a"  'calendar-beginning-of-week)
+  (define-key calendar-mode-map "\C-e"  'calendar-end-of-week)
+  (define-key calendar-mode-map "\ea"   'calendar-beginning-of-month)
+  (define-key calendar-mode-map "\ee"   'calendar-end-of-month)
+  (define-key calendar-mode-map "\e<"   'calendar-beginning-of-year)
+  (define-key calendar-mode-map "\e>"   'calendar-end-of-year)
+  (define-key calendar-mode-map "\C-@"  'calendar-set-mark)
+  (define-key calendar-mode-map "\C-x\C-x" 'calendar-exchange-point-and-mark)
+  (define-key calendar-mode-map "\e="   'calendar-count-days-region)
+  (define-key calendar-mode-map "gd"    'calendar-goto-date)
+  (define-key calendar-mode-map "gJ"    'calendar-goto-julian-date)
+  (define-key calendar-mode-map "gH"    'calendar-goto-hebrew-date)
+  (define-key calendar-mode-map "gI"    'calendar-goto-islamic-date)
+  (define-key calendar-mode-map "gC"    'calendar-goto-iso-date)
+  (define-key calendar-mode-map " "     'scroll-other-window)
+  (define-key calendar-mode-map "\C-c\C-l" 'redraw-calendar)
+  (define-key calendar-mode-map "c"     'calendar-current-month)
+  (define-key calendar-mode-map "o"     'calendar-other-month)
+  (define-key calendar-mode-map "q"     'exit-calendar)
+  (define-key calendar-mode-map "a"     'list-calendar-holidays)
+  (define-key calendar-mode-map "h"     'calendar-cursor-holidays)
+  (define-key calendar-mode-map "x"     'mark-calendar-holidays)
+  (define-key calendar-mode-map "u"     'calendar-unmark)
+  (define-key calendar-mode-map "m"     'mark-diary-entries)
+  (define-key calendar-mode-map "d"     'view-diary-entries)
+  (define-key calendar-mode-map "s"     'show-all-diary-entries)
+  (define-key calendar-mode-map "D"     'cursor-to-calendar-day-of-year)
+  (define-key calendar-mode-map "C"     'cursor-to-iso-calendar-date)
+  (define-key calendar-mode-map "J"     'cursor-to-julian-calendar-date)
+  (define-key calendar-mode-map "H"     'cursor-to-hebrew-calendar-date)
+  (define-key calendar-mode-map "I"     'cursor-to-islamic-calendar-date)
+  (define-key calendar-mode-map "F"     'cursor-to-french-calendar-date)
+  (define-key calendar-mode-map "\C-cd" 'insert-diary-entry)
+  (define-key calendar-mode-map "\C-cw" 'insert-weekly-diary-entry)
+  (define-key calendar-mode-map "\C-cm" 'insert-monthly-diary-entry)
+  (define-key calendar-mode-map "\C-cy" 'insert-yearly-diary-entry)
+  (define-key calendar-mode-map "\C-ca" 'insert-anniversary-diary-entry)
+  (define-key calendar-mode-map "\C-cb" 'insert-block-diary-entry)
+  (define-key calendar-mode-map "\C-cc" 'insert-cyclic-diary-entry)
+  (define-key calendar-mode-map "\C-cHd" 'insert-hebrew-diary-entry)
+  (define-key calendar-mode-map "\C-cHm" 'insert-monthly-hebrew-diary-entry)
+  (define-key calendar-mode-map "\C-cHy" 'insert-yearly-hebrew-diary-entry)
+  (define-key calendar-mode-map "\C-cId" 'insert-islamic-diary-entry)
+  (define-key calendar-mode-map "\C-cIm" 'insert-monthly-islamic-diary-entry)
+  (define-key calendar-mode-map "\C-cIy" 'insert-yearly-islamic-diary-entry)
+  (define-key calendar-mode-map "?"      'describe-calendar-mode))
+
+(defun describe-calendar-mode ()
+  "Create a help buffer with a brief description of the calendar-mode."
+  (interactive)
+  (with-output-to-temp-buffer "*Help*"
+    (princ
+     (format
+      "Calendar Mode:\nFor a complete description, type %s\n%s\n"
+      (substitute-command-keys
+       "\\<calendar-mode-map>\\[describe-mode] from within the calendar")
+      (substitute-command-keys "\\{calendar-mode-map}")))
+    (print-help-return-message)))
+
+;; Calendar mode is suitable only for specially formatted data.
+(put 'calendar-mode 'mode-class 'special)
+
+(defvar calendar-mode-line-format
+  (substitute-command-keys
+    "\\<calendar-mode-map>\\[scroll-calendar-left]      Calendar    \\[describe-calendar-mode] help/\\[calendar-other-month] other/\\[calendar-current-month] current    %17s       \\[scroll-calendar-right]")
+  "The mode line of the calendar buffer.")
+
+(defun calendar-mode ()
+  "A major mode for the sliding calendar window and diary.
+
+The commands for cursor movement are:\\<calendar-mode-map>
+
+       \\[calendar-forward-day]  one day forward           \\[calendar-backward-day]  one day backward
+       \\[calendar-forward-week]  one week forward          \\[calendar-backward-week]  one week backward
+       \\[calendar-forward-month]  one month forward       \\[calendar-backward-month]  one month backward
+       \\[calendar-forward-year]  one year forward        \\[calendar-backward-year]  one year backward
+       \\[calendar-beginning-of-week]  beginning of week         \\[calendar-end-of-week]  end of week
+       \\[calendar-beginning-of-month]  beginning of month      \\[calendar-end-of-month]  end of month
+       \\[calendar-beginning-of-year]  beginning of year       \\[calendar-end-of-year]  end of year
+       \\[calendar-goto-date]  go to date                \\[calendar-goto-julian-date]  go to Julian date
+       \\[calendar-goto-hebrew-date]  go to Hebrew date         \\[calendar-goto-islamic-date]  go to Islamic date
+       \\[calendar-goto-iso-date]  go to ISO date
+
+You can mark a date in the calendar and switch the point and mark:
+       \\[calendar-set-mark]  mark date                 \\[calendar-exchange-point-and-mark]  exchange point and mark
+You can determine the number of days (inclusive) between the point and mark by
+       \\[calendar-count-days-region]  count days in the region
+
+The commands for calendar movement are:
+
+       \\[scroll-calendar-right]  scroll one month right   \\[scroll-calendar-left]  scroll one month left
+       \\[scroll-calendar-right-three-months]  scroll 3 months right    \\[scroll-calendar-left-three-months]  scroll 3 months left
+       \\[calendar-current-month]  display current month        \\[calendar-other-month]  display another month
+
+Whenever it makes sense, the above commands take prefix arguments that
+multiply their affect.  For convenience, the digit keys and the minus sign
+are bound to digit-argument, so they need not be prefixed with ESC.
+
+If the calendar window somehow becomes corrupted, it can be regenerated with
+
+       \\[redraw-calendar]  redraw the calendar
+
+The following commands deal with holidays and other notable days:
+
+       \\[calendar-cursor-holidays]  give holidays for the date specified by the cursor
+       \\[mark-calendar-holidays]  mark notable days
+       \\[calendar-unmark]  unmark dates
+       \\[list-calendar-holidays]  display notable days
+
+The command M-x holidays causes the notable dates for the current month, and
+the preceding and succeeding months, to be displayed, independently of the
+calendar.
+
+The following commands control the diary:
+
+       \\[mark-diary-entries]  mark diary entries          \\[calendar-unmark]  unmark dates
+       \\[view-diary-entries]  display diary entries       \\[show-all-diary-entries]  show all diary entries
+       \\[print-diary-entries]  print diary entries
+
+Displaying the diary entries causes the diary entries from the diary-file
+(for the date indicated by the cursor in the calendar window) to be
+displayed in another window.  This function takes an integer argument that
+specifies the number of days of calendar entries to be displayed, starting
+with the date indicated by the cursor.
+
+The command \\[print-diary-entries] prints the diary buffer (as it appears)
+on the line printer.
+
+The command M-x diary causes the diary entries for the current date to be
+displayed, independently of the calendar.  The number of days of entries is
+governed by number-of-diary-entries.
+
+The format of the entries in the diary file is described in the
+documentation string for the variable diary-file.
+
+When diary entries are in view in the window, they can be edited.  It is
+important to keep in mind that the buffer displayed contains the entire
+diary file, but with portions of it concealed from view.  This means, for
+instance, that the forward-char command can put the cursor at what appears
+to be the end of the line, but what is in reality the middle of some
+concealed line.  BE CAREFUL WHEN EDITING THE DIARY ENTRIES! (Inserting
+additional lines or adding/deleting characters in the middle of a visible
+line will not cause problems; watch out for end-of-line, however--it may
+put you at the end of a concealed line far from where the cursor appears to
+be!)  BEFORE EDITING THE DIARY IT IS BEST TO DISPLAY THE ENTIRE FILE WITH
+show-all-diary-entries.  BE SURE TO WRITE THE FILE BEFORE EXITING FROM THE
+CALENDAR.
+
+The following commands assist in making diary entries:
+
+       \\[insert-diary-entry]  insert a diary entry for the selected date
+       \\[insert-weekly-diary-entry]  insert a diary entry for the selected day of the week
+       \\[insert-monthly-diary-entry]  insert a diary entry for the selected day of the month
+       \\[insert-yearly-diary-entry]  insert a diary entry for the selected day of the year
+       \\[insert-block-diary-entry]  insert a diary entry for the block days between point and mark
+       \\[insert-anniversary-diary-entry]  insert an anniversary diary entry for the selected date
+       \\[insert-cyclic-diary-entry]  insert a cyclic diary entry
+
+There are corresponding commands to assist in making Hebrew- or Islamic-date
+diary entries:
+
+       \\[insert-hebrew-diary-entry]  insert a diary entry for the Hebrew date corresponding
+                to the selected date
+       \\[insert-monthly-hebrew-diary-entry]  insert a diary entry for the day of the Hebrew month
+                corresponding to the selected day
+       \\[insert-yearly-hebrew-diary-entry]  insert a diary entry for the day of the Hebrew year
+                corresponding to the selected day
+       \\[insert-islamic-diary-entry]  insert a diary entry for the Islamic date corresponding
+                to the selected date
+       \\[insert-monthly-islamic-diary-entry]  insert a diary entry for the day of the Islamic month
+                corresponding to the selected day
+       \\[insert-yearly-islamic-diary-entry]  insert a diary entry for the day of the Islamic year
+                corresponding to the selected day
+
+All of the diary entry commands make nonmarking entries when given a prefix
+argument; with no prefix argument, the diary entries are marking.
+
+The day number in the year and the number of days remaining in the year can be
+determined by
+
+       \\[cursor-to-calendar-day-of-year]  show day number and the number of days remaining in the year
+
+Equivalent dates on the ISO commercial, Julian, Hebrew, Islamic and French
+Revolutionary calendars can be determined by
+
+       \\[cursor-to-iso-calendar-date]  show equivalent date on the ISO commercial calendar
+       \\[cursor-to-julian-calendar-date]  show equivalent date on the Julian calendar
+       \\[cursor-to-hebrew-calendar-date]  show equivalent date on the Hebrew calendar
+       \\[cursor-to-islamic-calendar-date]  show equivalent date on the Islamic calendar
+       \\[cursor-to-french-calendar-date]  show equivalent date on the French Revolutionary calendar
+
+To exit from the calendar use
+
+       \\[exit-calendar]  exit from calendar
+
+The variable `view-diary-entries-initially', whose default is nil, can be
+set to to t cause diary entries for the current date will be displayed in
+another window when the calendar is first displayed, if the current date is
+visible.  The variable `number-of-diary-entries' controls number of days of
+diary entries that will be displayed initially or with the command M-x
+diary.  For example, if the default value 1 is used, then only the current
+day's diary entries will be displayed.  If the value 2 is used, both the
+current day's and the next day's entries will be displayed.  The value can
+also be a vector: If the value is [0 2 2 2 2 4 1] then no diary entries
+will be displayed on Sunday, the current date's and the next day's diary
+entries will be displayed Monday through Thursday, Friday through Monday's
+entries will be displayed on Friday, while on Saturday only that day's
+entries will be displayed.
+
+The variable `view-calendar-holidays-initially' can be set to t to cause
+the holidays for the current three month period will be displayed on entry
+to the calendar.  The holidays are displayed in another window.
+
+The variable `mark-diary-entries-in-calendar' can be set to t to cause any
+dates visible with calendar entries to be marked with the symbol specified
+by the variable `diary-entry-marker', normally a plus sign.
+
+The variable `initial-calendar-window-hook', whose default value is nil,
+is list of functions to be called when the calendar window is first opened.
+The functions invoked are called after the calendar window is opened, but
+once opened is never called again.  Leaving the calendar with the `q' command
+and reentering it will cause these functions to be called again.
+
+The variable `today-visible-calendar-hook', whose default value is nil,
+is the list of functions called after the calendar buffer has been prepared
+with the calendar when the current date is visible in the window.
+This can be used, for example, to replace today's date with asterisks; a
+function calendar-star-date is included for this purpose:
+    (setq today-visible-calendar-hook 'calendar-star-date)
+It could also be used to mark the current date with `*'; a function is also
+provided for this:
+    (setq today-visible-calendar-hook 'calendar-mark-today)
+
+The variable `today-invisible-calendar-hook', whose default value is nil,
+is the list of functions called after the calendar buffer has been prepared
+with the calendar when the current date is not visible in the window.
+
+The variable `diary-display-hook' is the list of functions called
+after the diary buffer is prepared.  The default value simply displays the
+diary file using selective-display to conceal irrelevant diary entries.  An
+alternative function `fancy-diary-display' is provided that, when
+used as the `diary-display-hook', causes a noneditable buffer to be
+prepared with a neatly organized day-by-day listing of relevant diary
+entries, together with any known holidays.  The inclusion of the holidays
+slows this fancy display of the diary; to speed it up, set the variable
+`holidays-in-diary-buffer' to nil.
+
+The variable `print-diary-entries-hook' is the list of functions called
+after a temporary buffer is prepared with the diary entries currently
+visible in the diary buffer.  The default value of this hook adds a heading
+(composed from the diary buffer's mode line), does the printing with the
+command lpr-buffer, and kills the temporary buffer.  Other uses might
+include, for example, rearranging the lines into order by day and time.
+
+The Gregorian calendar is assumed."
+
+  (kill-all-local-variables)
+  (setq major-mode 'calendar-mode)
+  (setq mode-name "Calendar")
+  (use-local-map calendar-mode-map)
+  (setq buffer-read-only t)
+  (setq indent-tabs-mode nil)
+  (make-local-variable 'calendar-window-configuration);; Windows on entry.
+  (make-local-variable 'calendar-mark-ring)
+  (make-local-variable 'current-month)  ;;  Current month.
+  (make-local-variable 'current-day)    ;;  Current day.
+  (make-local-variable 'current-year)   ;;  Current year.
+  (make-local-variable 'displayed-month);;  Month in middle of window.
+  (make-local-variable 'displayed-year));;  Year in middle of window.
+
+(defun update-calendar-mode-line ()
+  "Update the calendar mode line with the current date and date style."
+  (if (bufferp (get-buffer calendar-buffer))
+      (save-excursion
+        (set-buffer calendar-buffer)
+        (setq mode-line-format
+              (format calendar-mode-line-format
+                      (calendar-date-string (calendar-current-date) t))))))
+
+(defun exit-calendar ()
+  "Get out of the calendar window and destroy it and related buffers."
+  (interactive)
+  (let ((diary-buffer (get-file-buffer diary-file))
+        (d-buffer (get-buffer fancy-diary-buffer))
+        (h-buffer (get-buffer holiday-buffer)))
+    (if (not diary-buffer)
+        (progn
+          (set-window-configuration calendar-window-configuration)
+          (kill-buffer calendar-buffer)
+          (if d-buffer (kill-buffer d-buffer))
+          (if h-buffer (kill-buffer h-buffer)))
+      (if (or (not (buffer-modified-p diary-buffer))
+              (yes-or-no-p "Diary modified; do you really want to exit the calendar? "))
+          (progn
+            (set-window-configuration calendar-window-configuration)
+            (kill-buffer calendar-buffer)
+            (if d-buffer (kill-buffer d-buffer))
+            (if h-buffer (kill-buffer h-buffer))
+            (set-buffer diary-buffer)
+            (set-buffer-modified-p nil)
+            (kill-buffer diary-buffer))))))
+
+(defun calendar-current-month ()
+  "Reposition the calendar window so the current date is visible."
+  (interactive)
+  (let ((today (calendar-current-date)));; The date might have changed.
+    (if (not (calendar-date-is-visible-p today))
+        (regenerate-calendar-window)
+      (update-calendar-mode-line)
+      (calendar-cursor-to-visible-date today))))
+
+(defun calendar-forward-month (arg)
+  "Move the cursor forward ARG months.
+Movement is backward if ARG is negative."
+  (interactive "p")
+  (calendar-cursor-to-nearest-date)
+  (let* ((cursor-date (or (calendar-cursor-to-date)
+                          (error "Cursor is not on a date!")))
+         (month (extract-calendar-month cursor-date))
+         (day (extract-calendar-day cursor-date))
+         (year (extract-calendar-year cursor-date)))
+    (increment-calendar-month month year arg)
+    (let ((last (calendar-last-day-of-month month year)))
+      (if (< last day)
+        (setq day last)))
+    ;; Put the new month on the screen, if needed, and go to the new date.
+    (let ((new-cursor-date (list month day year)))
+      (if (not (calendar-date-is-visible-p new-cursor-date))
+          (calendar-other-month month year))
+      (calendar-cursor-to-visible-date new-cursor-date))))
+
+(defun calendar-forward-year (arg)
+  "Move the cursor forward by ARG years.
+Movement is backward if ARG is negative."
+  (interactive "p")
+  (calendar-forward-month (* 12 arg)))
+
+(defun calendar-backward-month (arg)
+  "Move the cursor backward by ARG months.
+Movement is forward if ARG is negative."
+  (interactive "p")
+  (calendar-forward-month (- arg)))
+
+(defun calendar-backward-year (arg)
+  "Move the cursor backward ARG years.
+Movement is forward is ARG is negative."
+  (interactive "p")
+  (calendar-forward-month (* -12 arg)))
+
+(defun scroll-calendar-left (arg)
+  "Scroll the displayed calendar left by ARG months.
+If ARG is negative the calendar is scrolled right.  Maintains the relative
+position of the cursor with respect to the calendar as well as possible."
+  (interactive "p")
+  (calendar-cursor-to-nearest-date)
+  (let ((old-date (calendar-cursor-to-date))
+        (today (calendar-current-date)))
+    (if (/= arg 0)
+        (progn
+          (regenerate-calendar-window
+           (+ arg (calendar-interval current-month current-year
+                                     displayed-month displayed-year)))
+          (calendar-cursor-to-visible-date
+           (cond
+            ((calendar-date-is-visible-p old-date) old-date)
+            ((calendar-date-is-visible-p today) today)
+            (t (list displayed-month 1 displayed-year))))))))
+
+(defun scroll-calendar-right (arg)
+  "Scroll the displayed calendar window right by ARG months.
+If ARG is negative the calendar is scrolled left.  Maintains the relative
+position of the cursor with respect to the calendar as well as possible."
+  (interactive "p")
+  (scroll-calendar-left (- arg)))
+
+(defun scroll-calendar-left-three-months (arg)
+  "Scroll the displayed calendar window left by 3*ARG months.
+If ARG is negative the calendar is scrolled right.  Maintains the relative
+position of the cursor with respect to the calendar as well as possible."
+  (interactive "p")
+  (scroll-calendar-left (* 3 arg)))
+
+(defun scroll-calendar-right-three-months (arg)
+  "Scroll the displayed calendar window right by 3*ARG months.
+If ARG is negative the calendar is scrolled left.  Maintains the relative
+position of the cursor with respect to the calendar as well as possible."
+  (interactive "p")
+  (scroll-calendar-left (* -3 arg)))
+
+(defun calendar-current-date ()
+  "Returns the current date in a list (month day year).
+If in the calendar buffer, also sets the current date local variables."
+  (let* ((date (current-time-string))
+         (garbage
+          (string-match
+           "^\\([A-Z][a-z]*\\) *\\([A-Z][a-z]*\\) *\\([0-9]*\\) .* \\([0-9]*\\)$"
+           date))
+         (month
+          (cdr (assoc 
+                (substring date (match-beginning 2) (match-end 2))
+                (calendar-make-alist
+                 calendar-month-name-array
+                 1
+                 '(lambda (x) (substring x 0 3))))))
+         (day
+          (string-to-int (substring date (match-beginning 3) (match-end 3))))
+         (year
+          (string-to-int (substring date (match-beginning 4) (match-end 4)))))
+    (if (equal (current-buffer) (get-buffer calendar-buffer))
+      (progn
+        (setq current-month month)
+        (setq current-day day)
+        (setq current-year year)))
+    (list month day year)))
+
+(defun calendar-cursor-to-date ()
+  "Returns a list of the month, day, and year of current cursor position.
+Returns nil if the cursor is not on a specific day."
+  (if (and (looking-at "[*0-9]")
+           (< 2 (count-lines (point-min) (point))))
+      (save-excursion
+        (re-search-backward "[^0-9]")
+        (forward-char 1)
+        (let*
+            ((day (string-to-int (buffer-substring (point) (+ 3 (point)))))
+             (day (if (= 0 day) current-day day));; Starred date.
+             (segment (/ (current-column) 25))
+             (month (% (+ displayed-month segment -1) 12))
+             (month (if (= 0 month) 12 month))
+             (year
+              (cond
+               ((and (=  12 month) (= segment 0)) (1- displayed-year))
+               ((and (=   1 month) (= segment 2)) (1+ displayed-year))
+               (t displayed-year))))
+          (list month day year)))))
+
+(defun calendar-cursor-to-nearest-date ()
+  "Move the cursor to the closest date.
+The position of the cursor is unchanged if it is already on a date.
+Returns the list (month day year) giving the cursor position."
+  (let ((date (calendar-cursor-to-date))
+        (column (current-column)))
+    (if date
+        date
+      (if (> 3 (count-lines (point-min) (point)))
+          (progn
+            (goto-line 3)
+            (move-to-column column)))
+      (if (not (looking-at "[0-9]"))
+          (if (and (not (looking-at " *$"))
+                   (or (< column 25)
+                       (and (> column 27)
+                            (< column 50))
+                       (and (> column 52)
+                            (< column 75))))
+              (progn
+                (re-search-forward "[0-9]" nil t)
+                (backward-char 1))
+            (re-search-backward "[0-9]" nil t)))
+      (calendar-cursor-to-date))))
+
+(defun calendar-forward-day (arg)
+  "Move the cursor forward ARG days.
+Moves backward if ARG is negative."
+  (interactive "p")
+  (if (/= 0 arg)
+      (let*
+          ((cursor-date (calendar-cursor-to-date))
+           (cursor-date (if cursor-date
+                            cursor-date
+                          (if (> arg 0) (setq arg (1- arg)))
+                          (calendar-cursor-to-nearest-date)))
+           (new-cursor-date
+            (calendar-gregorian-from-absolute
+             (+ (calendar-absolute-from-gregorian cursor-date) arg)))
+           (new-display-month (extract-calendar-month new-cursor-date))
+           (new-display-year (extract-calendar-year new-cursor-date)))
+        ;; Put the new month on the screen, if needed, and go to the new date.
+        (if (not (calendar-date-is-visible-p new-cursor-date))
+            (calendar-other-month new-display-month new-display-year))
+        (calendar-cursor-to-visible-date new-cursor-date))))
+
+(defun calendar-backward-day (arg)
+  "Move the cursor back ARG days.
+Moves forward if ARG is negative."
+  (interactive "p")
+  (calendar-forward-day (- arg)))
+
+(defun calendar-forward-week (arg)
+  "Move the cursor forward ARG weeks.
+Moves backward if ARG is negative."
+  (interactive "p")
+  (calendar-forward-day (* arg 7)))
+
+(defun calendar-backward-week (arg)
+  "Move the cursor back ARG weeks.
+Moves forward if ARG is negative."
+  (interactive "p")
+  (calendar-forward-day (* arg -7)))
+
+(defun calendar-beginning-of-week (arg)
+  "Move the cursor back ARG Sundays."
+  (interactive "p")
+  (calendar-cursor-to-nearest-date)
+  (let ((day (calendar-day-of-week (calendar-cursor-to-date))))
+    (calendar-backward-day
+     (if (= day 0) (* 7 arg) (+ day (* 7 (1- arg)))))))
+
+(defun calendar-end-of-week (arg)
+  "Move the cursor forward ARG Saturdays."
+  (interactive "p")
+  (calendar-cursor-to-nearest-date)
+  (let ((day (calendar-day-of-week (calendar-cursor-to-date))))
+    (calendar-forward-day
+     (if (= day 6) (* 7 arg) (+ (- 6 day) (* 7 (1- arg)))))))
+
+(defun calendar-beginning-of-month (arg)
+  "Move the cursor backward ARG month beginnings."
+  (interactive "p")
+  (calendar-cursor-to-nearest-date)
+  (let* ((date (calendar-cursor-to-date))
+         (month (extract-calendar-month date))
+         (day (extract-calendar-day date))
+         (year (extract-calendar-year date)))
+    (if (= day 1)
+        (calendar-backward-month arg)
+      (calendar-cursor-to-visible-date (list month 1 year))
+      (calendar-backward-month (1- arg)))))
+
+(defun calendar-end-of-month (arg)
+  "Move the cursor forward ARG month ends."
+  (interactive "p")
+  (calendar-cursor-to-nearest-date)
+  (let* ((date (calendar-cursor-to-date))
+         (month (extract-calendar-month date))
+         (day (extract-calendar-day date))
+         (year (extract-calendar-year date))
+         (last-day (calendar-last-day-of-month month year)))
+    (if (/= day last-day)
+        (progn
+          (calendar-cursor-to-visible-date (list month last-day year))
+          (setq arg (1- arg))))
+    (increment-calendar-month month year arg)
+    (let ((last-day (list
+                     month
+                     (calendar-last-day-of-month month year)
+                     year)))
+      (if (not (calendar-date-is-visible-p last-day))
+          (calendar-other-month month year)
+      (calendar-cursor-to-visible-date last-day)))))
+
+(defun calendar-beginning-of-year (arg)
+  "Move the cursor backward ARG year beginnings."
+  (interactive "p")
+  (calendar-cursor-to-nearest-date)
+  (let* ((date (calendar-cursor-to-date))
+         (month (extract-calendar-month date))
+         (day (extract-calendar-day date))
+         (year (extract-calendar-year date))
+         (jan-first (list 1 1 year)))
+    (if (and (= day 1) (= 1 month))
+        (calendar-backward-month (* 12 arg))
+      (if (and (= arg 1)
+               (calendar-date-is-visible-p jan-first))
+          (calendar-cursor-to-visible-date jan-first)
+        (calendar-other-month 1 (- year (1- arg)))))))
+
+(defun calendar-end-of-year (arg)
+  "Move the cursor forward ARG year beginnings."
+  (interactive "p")
+  (calendar-cursor-to-nearest-date)
+  (let* ((date (calendar-cursor-to-date))
+         (month (extract-calendar-month date))
+         (day (extract-calendar-day date))
+         (year (extract-calendar-year date))
+         (dec-31 (list 12 31 year)))
+    (if (and (= day 31) (= 12 month))
+        (calendar-forward-month (* 12 arg))
+      (if (and (= arg 1)
+               (calendar-date-is-visible-p dec-31))
+          (calendar-cursor-to-visible-date dec-31)
+        (calendar-other-month 12 (- year (1- arg)))
+        (calendar-cursor-to-visible-date (list 12 31 displayed-year))))))
+
+(defun calendar-gregorian-from-absolute (date)
+  "Compute the list (month day year) corresponding to the absolute DATE.
+The absolute date is the number of days elapsed since the (imaginary)
+Gregorian date Sunday, December 31, 1 BC."
+  (let* ((approx (/ date 366));; Approximation from below.
+         (year                ;; Search forward from the approximation.
+          (+ approx
+             (calendar-sum y approx
+                 (>= date (calendar-absolute-from-gregorian (list 1 1 (1+ y))))
+                  1)))
+         (month         ;; Search forward from January.
+          (1+ (calendar-sum m 1
+                   (> date
+                      (calendar-absolute-from-gregorian
+                       (list m (calendar-last-day-of-month m year) year)))
+                   1)))
+         (day           ;; Calculate the day by subtraction.
+          (- date
+             (1- (calendar-absolute-from-gregorian (list month 1 year))))))
+    (list month day year)))
+
+(defun calendar-cursor-to-visible-date (date)
+  "Move the cursor to DATE that is on the screen."
+    (let ((month (extract-calendar-month date))
+          (day (extract-calendar-day date))
+          (year (extract-calendar-year date)))
+      (goto-line (+ 3
+                    (/ (+ day -1
+                          (calendar-day-of-week (list month 1 year)))
+                       7)))
+      (move-to-column (+ 6
+                         (* 25
+                            (1+ (calendar-interval
+                                 displayed-month displayed-year month year)))
+                         (* 3 (calendar-day-of-week date))))))
+
+(defun calendar-other-month (month year)
+  "Display a three-month calendar centered around MONTH and YEAR."
+  (interactive
+   (let* ((completion-ignore-case t)
+          (month (cdr (assoc
+                       (capitalize
+                        (completing-read
+                         "Month name: "
+                         (mapcar 'list (append calendar-month-name-array nil))
+                         nil t))
+                       (calendar-make-alist calendar-month-name-array))))
+          (year (calendar-read
+                 "Year (>0): "
+                 '(lambda (x) (> x 0))
+                 (int-to-string current-year))))
+     (list month year)))
+  (if (and (= month displayed-month)
+           (= year displayed-year))
+      nil
+    (let ((old-date (calendar-cursor-to-date))
+          (today (calendar-current-date)))
+      (regenerate-calendar-window
+       (calendar-interval current-month current-year month year))
+      (calendar-cursor-to-visible-date
+       (cond
+        ((calendar-date-is-visible-p old-date) old-date)
+        ((calendar-date-is-visible-p today) today)
+        (t (list month 1 year)))))))
+
+(defun calendar-set-mark (arg)
+  "Mark the date under the cursor, or jump to marked date.
+With no prefix argument, push current date onto marked date ring.
+With argument, jump to mark, pop it, and put point at end of ring."
+  (interactive "P")
+  (let ((date (or (calendar-cursor-to-date)
+                  (error "Cursor is not on a date!"))))
+    (if (null arg)
+        (progn
+          (setq calendar-mark-ring (cons date calendar-mark-ring))
+          ;; Since the top of the mark ring is the marked date in the
+          ;; calendar, the mark ring in the calendar is one longer than
+          ;; in other buffers to get the same effect.
+          (if (> (length calendar-mark-ring) (1+ mark-ring-max))
+              (setcdr (nthcdr mark-ring-max calendar-mark-ring) nil))
+          (message "Mark set"))
+      (if (null calendar-mark-ring)
+          (error "No mark set in this buffer")
+        (calendar-goto-date (car calendar-mark-ring))
+        (setq calendar-mark-ring
+              (cdr (nconc calendar-mark-ring (list date))))))))
+
+(defun calendar-exchange-point-and-mark ()
+  "Exchange the current cursor position with the marked date."
+  (interactive)
+  (let ((mark (car calendar-mark-ring))
+        (date (or (calendar-cursor-to-date)
+                  (error "Cursor is not on a date!"))))
+    (if (null mark)
+        (error "No mark set in this buffer")
+      (setq calendar-mark-ring (cons date (cdr calendar-mark-ring)))
+      (calendar-goto-date mark))))
+
+(defun calendar-count-days-region ()
+  "Count the number of days (inclusive) between point and the mark."
+  (interactive)
+  (let* ((days (- (calendar-absolute-from-gregorian
+                   (or (calendar-cursor-to-date)
+                       (error "Cursor is not on a date!")))
+                  (calendar-absolute-from-gregorian
+                   (or (car calendar-mark-ring)
+                       (error "No mark set in this buffer")))))
+         (days (1+ (if (> days 0) days (- days)))))
+    (message "Region has %d day%s (inclusive)"
+             days (if (> days 1) "s" ""))))
+
+(defun calendar-not-implemented ()
+  "Not implemented."
+  (interactive)
+  (error "%s not available in the calendar"
+         (global-key-binding (this-command-keys))))
+
+(defun calendar-read (prompt acceptable &optional initial-contents)
+  "Return an object read from the minibuffer.
+Prompt with the string PROMPT and use the function ACCEPTABLE to decide if
+entered item is acceptable.  If non-nil, optional third arg INITIAL-CONTENTS
+is a string to insert in the minibuffer before reading."
+  (let ((value (read-minibuffer prompt initial-contents)))
+    (while (not (funcall acceptable value))
+      (setq value (read-minibuffer prompt initial-contents)))
+    value))
+
+(defun calendar-goto-date (date)
+  "Move cursor to DATE."
+  (interactive
+   (let* ((year (calendar-read
+                 "Year (>0): "
+                 '(lambda (x) (> x 0))
+                 (int-to-string current-year)))
+          (month-array calendar-month-name-array)
+          (completion-ignore-case t)
+          (month (cdr (assoc
+                       (capitalize
+                        (completing-read
+                         "Month name: "
+                         (mapcar 'list (append month-array nil))
+                         nil t))
+                       (calendar-make-alist month-array 1 'capitalize))))
+          (last (calendar-last-day-of-month month year))
+          (day (calendar-read
+                (format "Day (1-%d): " last)
+                '(lambda (x) (and (< 0 x) (<= x last))))))
+     (list (list month day year))))
+  (let ((month (extract-calendar-month date))
+        (year (extract-calendar-year date)))
+    (if (not (calendar-date-is-visible-p date))
+        (calendar-other-month
+         (if (and (= month 1) (= year 1))
+             2
+           month)
+         year)))
+  (calendar-cursor-to-visible-date date))
+
+(defun calendar-goto-julian-date (date &optional noecho)
+  "Move cursor to Julian DATE; echo Julian date unless NOECHO is t."
+  (interactive
+   (let* ((year (calendar-read
+                 "Julian calendar year (>0): "
+                 '(lambda (x) (> x 0))
+                 (int-to-string
+                  (extract-calendar-year
+                   (calendar-julian-from-absolute
+                    (calendar-absolute-from-gregorian
+                     (list current-month 1 current-year)))))))
+          (month-array calendar-month-name-array)
+          (completion-ignore-case t)
+          (month (cdr (assoc
+                       (capitalize
+                        (completing-read
+                         "Julian calendar month name: "
+                         (mapcar 'list (append month-array nil))
+                         nil t))
+                       (calendar-make-alist month-array 1 'capitalize))))
+          (last 
+           (if (and (zerop (% year 4)) (= month 2))
+               29
+             (aref [31 28 31 30 31 30 31 31 30 31 30 31] (1- month))))
+          (day (calendar-read
+                (format "Julian calendar day (%d-%d): "
+                        (if (and (= year 1) (= month 1)) 3 1) last)
+                '(lambda (x) 
+                   (and (< (if (and (= year 1) (= month 1)) 2 0) x)
+                        (<= x last))))))
+     (list (list month day year))))
+  (calendar-goto-date (calendar-gregorian-from-absolute
+                       (calendar-absolute-from-julian date)))
+  (or noecho (cursor-to-julian-calendar-date)))
+
+(defun calendar-goto-hebrew-date (date &optional noecho)
+  "Move cursor to Hebrew DATE; echo Hebrew date unless NOECHO is t."
+  (interactive
+   (let* ((year (calendar-read
+                 "Hebrew calendar year (>3760): "
+                 '(lambda (x) (> x 3760))
+                 (int-to-string
+                  (extract-calendar-year
+                   (calendar-hebrew-from-absolute
+                    (calendar-absolute-from-gregorian
+                     (list current-month 1 current-year)))))))
+          (month-array (if (hebrew-calendar-leap-year-p year)
+                           calendar-hebrew-month-name-array-leap-year
+                         calendar-hebrew-month-name-array-common-year))
+          (completion-ignore-case t)
+          (month (cdr (assoc
+                       (capitalize
+                        (completing-read
+                         "Hebrew calendar month name: "
+                         (mapcar 'list (append month-array nil))
+                         (if (= year 3761)
+                             '(lambda (x)
+                                (let ((m (cdr
+                                          (assoc
+                                           (car x)
+                                           (calendar-make-alist
+                                            month-array)))))
+                                  (< 0
+                                     (calendar-absolute-from-hebrew
+                                      (list m
+                                            (hebrew-calendar-last-day-of-month
+                                             m year)
+                                            year))))))
+                                 
+                         t))
+                       (calendar-make-alist month-array 1 'capitalize))))
+          (last (hebrew-calendar-last-day-of-month month year))
+          (first (if (and (= year 3761) (= month 10))
+                     18 1))
+          (day (calendar-read
+                (format "Hebrew calendar day (%d-%d): "
+                        first last)
+                '(lambda (x) (and (<= first x) (<= x last))))))
+     (list (list month day year))))
+  (calendar-goto-date (calendar-gregorian-from-absolute
+                       (calendar-absolute-from-hebrew date)))
+  (or noecho (cursor-to-hebrew-calendar-date)))
+
+(defun calendar-goto-islamic-date (date &optional noecho)
+  "Move cursor to Islamic DATE; echo Islamic date unless NOECHO is t."
+  (interactive
+   (let* ((year (calendar-read
+                 "Islamic calendar year (>0): "
+                 '(lambda (x) (> x 0))
+                 (int-to-string
+                  (extract-calendar-year
+                   (calendar-islamic-from-absolute
+                    (calendar-absolute-from-gregorian
+                     (list current-month 1 current-year)))))))
+          (month-array calendar-islamic-month-name-array)
+          (completion-ignore-case t)
+          (month (cdr (assoc
+                       (capitalize
+                        (completing-read
+                         "Islamic calendar month name: "
+                         (mapcar 'list (append month-array nil))
+                         nil t))
+                       (calendar-make-alist month-array 1 'capitalize))))
+          (last (islamic-calendar-last-day-of-month month year))
+          (day (calendar-read
+                (format "Islamic calendar day (1-%d): " last)
+                '(lambda (x) (and (< 0 x) (<= x last))))))
+     (list (list month day year))))
+  (calendar-goto-date (calendar-gregorian-from-absolute
+                       (calendar-absolute-from-islamic date)))
+  (or noecho (cursor-to-islamic-calendar-date)))
+
+(defun calendar-goto-iso-date (date &optional noecho)
+  "Move cursor to ISO DATE; echo ISO date unless NOECHO is t."
+  (interactive
+   (let* ((year (calendar-read
+                 "ISO calendar year (>0): "
+                 '(lambda (x) (> x 0))
+                 (int-to-string current-year)))
+          (no-weeks (extract-calendar-month
+                     (calendar-iso-from-absolute
+                      (1-
+                       (calendar-dayname-on-or-before
+                        1 (calendar-absolute-from-gregorian
+                           (list 1 4 (1+ year))))))))
+          (week (calendar-read
+                 (format "ISO calendar week (1-%d): " no-weeks)
+                 '(lambda (x) (and (> x 0) (<= x no-weeks)))))
+          (day (calendar-read
+                "ISO day (1-7): "
+                '(lambda (x) (and (<= 1 x) (<= x 7))))))
+     (list (list week day year))))
+  (calendar-goto-date (calendar-gregorian-from-absolute
+                       (calendar-absolute-from-iso date)))
+  (or noecho (cursor-to-iso-calendar-date)))
+
+(defun calendar-interval (mon1 yr1 mon2 yr2)
+  "The number of months difference between the two specified months."
+  (+ (* 12 (- yr2 yr1))
+     (- mon2 mon1)))
+
+(defun calendar-leap-year-p (year)
+  "Returns t if YEAR is a Gregorian leap year."
+  (or
+    (and (=  (% year   4) 0)
+         (/= (% year 100) 0))
+    (= (% year 400) 0)))
+
+(defun calendar-day-number (date)
+  "Return the day number within the year of the date DATE.
+For example, (calendar-day-number '(1 1 1987)) returns the value 1,
+while (calendar-day-number '(12 31 1980)) returns 366."
+;;
+;; An explanation of the calculation can be found in PascAlgorithms by
+;; Edward and Ruth Reingold, Scott-Foresman/Little, Brown, 1988.
+;;
+    (let* ((month (extract-calendar-month date))
+           (day (extract-calendar-day date))
+           (year (extract-calendar-year date))
+         (day-of-year (+ day (* 31 (1- month)))))
+      (if (> month 2)
+          (progn
+            (setq day-of-year (- day-of-year (/ (+ 23 (* 4 month)) 10)))
+            (if (calendar-leap-year-p year)
+                (setq day-of-year (1+ day-of-year)))))
+      day-of-year))
+
+(defun calendar-day-name (date)
+  "Returns a string with the name of the day of the week of DATE."
+  (aref calendar-day-name-array (calendar-day-of-week date)))
+
+(defconst calendar-day-name-array
+  ["Sunday" "Monday" "Tuesday" "Wednesday" "Thursday" "Friday" "Saturday"])
+
+(defun calendar-last-day-of-month (month year)
+  "The last day in MONTH during YEAR."
+  (if (and (calendar-leap-year-p year) (= month 2))
+      29
+    (aref [31 28 31 30 31 30 31 31 30 31 30 31] (1- month))))
+
+(defconst calendar-month-name-array
+  ["January" "February" "March"     "April"   "May"      "June"
+   "July"    "August"   "September" "October" "November" "December"])
+
+(defun calendar-make-alist (sequence &optional start-index filter)
+  "Make an assoc list corresponding to SEQUENCE.
+Start at index 1, unless optional START-INDEX is provided.
+If FILTER is provided, apply it to each item in the list."
+  (let ((index (if start-index (1- start-index) 0)))
+    (mapcar
+     '(lambda (x)
+        (setq index (1+ index))
+        (cons (if filter (funcall filter x) x)
+              index))
+     (append sequence nil))))
+
+(defun calendar-month-name (month)
+  "The name of MONTH."
+  (aref calendar-month-name-array (1- month)))
+
+(defun calendar-day-of-week (date)
+  "Returns the day-of-the-week index of DATE, 0 for Sunday, 1 for Monday, etc."
+  (% (calendar-absolute-from-gregorian date) 7))
+
+(defun calendar-absolute-from-gregorian (date)
+  "The number of days elapsed between the Gregorian date 12/31/1 BC and DATE.
+The Gregorian date Sunday, December 31, 1 BC is imaginary."
+  (let ((month (extract-calendar-month date))
+        (day (extract-calendar-day date))
+        (year (extract-calendar-year date)))
+    (+ (calendar-day-number date);; Days this year
+       (* 365 (1- year));;        + Days in prior years
+       (/ (1- year) 4);;          + Julian leap years
+       (- (/ (1- year) 100));;    - century years
+       (/ (1- year) 400))));;     + Gregorian leap years
+
+(defun calendar-unmark ()
+  "Delete the diary and holiday marks from the calendar."
+  (interactive)
+  (setq mark-diary-entries-in-calendar nil)
+  (setq mark-holidays-in-calendar nil)
+  (save-excursion
+    (goto-line 3)
+    (beginning-of-line)
+    (let ((buffer-read-only nil)
+          (start (point))
+          (star-date (search-forward "**" nil t))
+          (star-point (point)))
+      (if star-date
+          (progn    ;;  Don't delete today as left by calendar-star-date
+            (subst-char-in-region start (- star-point 2)
+                                  (string-to-char diary-entry-marker) ?  t)
+            (subst-char-in-region start (- star-point 2)
+                                 (string-to-char calendar-holiday-marker) ?  t)
+            (subst-char-in-region star-point (point-max)
+                                  (string-to-char diary-entry-marker) ?  t)
+            (subst-char-in-region star-point (point-max)
+                                (string-to-char calendar-holiday-marker) ?  t))
+        (subst-char-in-region start (point-max)
+                              (string-to-char diary-entry-marker) ?  t)
+        (subst-char-in-region start (point-max)
+                              (string-to-char calendar-holiday-marker) ?  t))
+      (set-buffer-modified-p nil))))
+
+(defun calendar-date-is-visible-p (date)
+  "Returns t if DATE is legal and is visible in the calendar window."
+  (let ((gap (calendar-interval
+              displayed-month displayed-year
+              (extract-calendar-month date) (extract-calendar-year date))))
+    (and (calendar-date-is-legal-p date) (> 2 gap) (< -2 gap))))
+
+(defun calendar-date-is-legal-p (date)
+  "Returns t if DATE is a legal date."
+  (let ((month (extract-calendar-month date))
+        (day (extract-calendar-day date))
+        (year (extract-calendar-year date)))
+    (and (<= 1 month) (<= month 12)
+         (<= 1 day) (<= day (calendar-last-day-of-month month year))
+         (<= 1 year))))
+
+(defun calendar-date-equal (date1 date2)
+  "Returns t if the DATE1 and DATE2 are the same."
+  (and
+   (= (extract-calendar-month date1) (extract-calendar-month date2))
+   (= (extract-calendar-day date1) (extract-calendar-day date2))
+   (= (extract-calendar-year date1) (extract-calendar-year date2))))
+
+(defun mark-visible-calendar-date (date &optional mark)
+  "Leave mark DATE with MARK.  MARK defaults to diary-entry-marker."
+  (if (calendar-date-is-legal-p date)
+      (save-excursion
+        (set-buffer calendar-buffer)
+        (calendar-cursor-to-visible-date date)
+        (forward-char 1)
+        (let ((buffer-read-only nil))
+          (delete-char 1)
+          (insert (if mark mark diary-entry-marker))
+          (forward-char -2))
+        (set-buffer-modified-p nil))))
+
+(defun calendar-star-date ()
+  "Replace the date under the cursor in the calendar window with asterisks.
+This function can be used with the today-visible-calendar-hook run after the
+calendar window has been prepared."
+  (let ((buffer-read-only nil))
+    (forward-char 1)
+    (delete-char -2)
+    (insert "**")
+    (backward-char 1)
+    (set-buffer-modified-p nil)))
+
+(defun calendar-mark-today ()
+  "Mark the date under the cursor in the calendar window with an equal sign.
+This function can be used with the today-visible-calendar-hook run after the
+calendar window has been prepared."
+  (let ((buffer-read-only nil))
+    (forward-char 1)
+    (delete-char 1)
+    (insert "=")
+    (backward-char 2)
+    (set-buffer-modified-p nil)))
+
+(defun calendar-date-compare (date1 date2)
+  "Returns t if DATE1 is before DATE2, nil otherwise.
+The actual dates are in the car of DATE1 and DATE2."
+  (< (calendar-absolute-from-gregorian (car date1))
+     (calendar-absolute-from-gregorian (car date2))))
+
+(defun calendar-date-string (date &optional abbreviate nodayname)
+  "A string form of DATE, driven by the variable `calendar-date-display-form'.
+An optional parameter ABBREVIATE, when t, causes the month and day names to be
+abbreviated to three characters.  An optional parameter NODAYNAME, when t,
+omits the name of the day of the week."
+  (let* ((dayname
+          (if nodayname
+              ""
+            (if abbreviate
+                (substring (calendar-day-name date) 0 3)
+              (calendar-day-name date))))
+         (month (extract-calendar-month date))
+         (monthname
+          (if abbreviate
+              (substring
+               (calendar-month-name month) 0 3)
+            (calendar-month-name month)))
+         (day (int-to-string (extract-calendar-day date)))
+         (month (int-to-string month))
+         (year (int-to-string (extract-calendar-year date))))
+    (mapconcat 'eval calendar-date-display-form "")))
+
+(defun calendar-dayname-on-or-before (dayname date)
+  "Returns the absolute date of the DAYNAME on or before absolute DATE.
+DAYNAME=0 means Sunday, DAYNAME=1 means Monday, and so on.
+
+Note: Applying this function to d+6 gives us the DAYNAME on or after an
+absolute day d.  Similarly, applying it to d+3 gives the DAYNAME nearest to
+absolute date d, applying it to d-1 gives the DAYNAME previous to absolute
+date d, and applying it to d+7 gives the DAYNAME following absolute date d."
+  (- date (% (- date dayname) 7)))
+
+(defun calendar-nth-named-day (n dayname month year)
+  "Returns the date of the  Nth DAYNAME in MONTH, YEAR.
+A DAYNAME of 0 means Sunday, 1 means Monday, and so on.  If N<0, the
+date returned is the Nth DAYNAME from the end of MONTH, YEAR (that is, -1 is
+the last DAYNAME, -2 is the penultimate DAYNAME, and so on."
+  (calendar-gregorian-from-absolute
+   (if (> n 0)
+       (+ (calendar-dayname-on-or-before
+           dayname (calendar-absolute-from-gregorian (list month 7 year)))
+          (* 7 (1- n)))
+     (+ (calendar-dayname-on-or-before
+         dayname
+         (calendar-absolute-from-gregorian
+          (list month (calendar-last-day-of-month month year) year)))
+        (* 7 (1+ n))))))
+
+(defun cursor-to-calendar-day-of-year ()
+  "Show the day number in the year and the number of days remaining in the
+year for the date under the cursor."
+  (interactive)
+  (let* ((date (or (calendar-cursor-to-date)
+                   (error "Cursor is not on a date!")))
+         (year (extract-calendar-year date))
+         (day (calendar-day-number date))
+         (days-remaining (- (calendar-day-number (list 12 31 year)) day)))
+    (message "Day %d of %d; %d day%s remaining in the year"
+             day year days-remaining (if (= days-remaining 1) "" "s"))))
+
+(defun calendar-absolute-from-iso (date)
+  "The number of days elapsed between the Gregorian date 12/31/1 BC and
+DATE.  The `ISO year' corresponds approximately to the Gregorian year, but
+weeks start on Monday and end on Sunday.  The first week of the ISO year is
+the first such week in which at least 4 days are in a year.  The ISO
+commercial DATE has the form (week day year) in which week is in the range
+1..52 and day is in the range 0..6 (1 = Monday, 2 = Tuesday, ..., 0 =
+Sunday).  The The Gregorian date Sunday, December 31, 1 BC is imaginary."
+  (let* ((week (extract-calendar-month date))
+         (day (extract-calendar-day date))
+         (year (extract-calendar-year date)))
+    (+ (calendar-dayname-on-or-before
+        1 (+ 3 (calendar-absolute-from-gregorian (list 1 1 year))))
+       (* 7 (1- week))
+       (if (= day 0) 6 (1- day)))))
+
+(defun calendar-iso-from-absolute (date)
+  "Compute the `ISO commercial date' corresponding to the absolute DATE.
+The ISO year corresponds approximately to the Gregorian year, but weeks
+start on Monday and end on Sunday.  The first week of the ISO year is the
+first such week in which at least 4 days are in a year.  The ISO commercial
+date has the form (week day year) in which week is in the range 1..52 and
+day is in the range 0..6 (1 = Monday, 2 = Tuesday, ..., 0 = Sunday).  The
+absolute date is the number of days elapsed since the (imaginary) Gregorian
+date Sunday, December 31, 1 BC."
+  (let* ((approx (extract-calendar-year
+                  (calendar-gregorian-from-absolute (- date 3))))
+         (year (+ approx
+                  (calendar-sum y approx
+                      (>= date (calendar-absolute-from-iso (list 1 1 (1+ y))))
+                      1))))
+    (list
+     (1+ (/ (- date (calendar-absolute-from-iso (list 1 1 year))) 7))
+     (% date 7)
+     year)))
+
+(defun cursor-to-iso-calendar-date ()
+  "Show the equivalent date on the `ISO commercial calendar' for the date
+under the cursor."
+  (interactive)
+  (let* ((greg-date
+          (or (calendar-cursor-to-date)
+              (error "Cursor is not on a date!")))
+         (day (% (calendar-absolute-from-gregorian greg-date) 7))
+         (iso-date (calendar-iso-from-absolute
+                    (calendar-absolute-from-gregorian greg-date))))
+    (message "ISO date: Day %s of week %d of %d."
+             (if (zerop day) 7 day)
+             (extract-calendar-month iso-date)
+             (extract-calendar-year iso-date))))
+
+(defun calendar-julian-from-absolute (date)
+  "Compute the Julian (month day year) corresponding to the absolute DATE.
+The absolute date is the number of days elapsed since the (imaginary)
+Gregorian date Sunday, December 31, 1 BC."
+  (let* ((approx (/ (+ date 2) 366));; Approximation from below.
+         (year        ;; Search forward from the approximation.
+          (+ approx
+             (calendar-sum y approx
+                (>= date (calendar-absolute-from-julian (list 1 1 (1+ y))))
+                1)))
+         (month       ;; Search forward from January.
+          (1+ (calendar-sum m 1
+                 (> date
+                    (calendar-absolute-from-julian
+                     (list m
+                           (if (and (= m 2) (= (% year 4) 0))
+                               29
+                             (aref [31 28 31 30 31 30 31 31 30 31 30 31]
+                                   (1- m)))
+                           year)))
+                 1)))
+         (day         ;; Calculate the day by subtraction.
+          (- date (1- (calendar-absolute-from-julian (list month 1 year))))))
+    (list month day year)))
+
+(defun calendar-absolute-from-julian (date)
+  "The number of days elapsed between the Gregorian date 12/31/1 BC and DATE.
+The Gregorian date Sunday, December 31, 1 BC is imaginary."
+  (let ((month (extract-calendar-month date))
+        (day (extract-calendar-day date))
+        (year (extract-calendar-year date)))
+    (+ (calendar-day-number date)
+       (if (and (= (% year 100) 0)
+                (/= (% year 400) 0)
+                (> month 2))
+           1 0);; Correct for Julian but not Gregorian leap year.
+       (* 365 (1- year))
+       (/ (1- year) 4)
+       -2)))
+
+(defun cursor-to-julian-calendar-date ()
+  "Show the Julian calendar equivalent of the date under the cursor."
+  (interactive)
+  (let ((calendar-date-display-form
+         (if european-calendar-style
+             '(day " " monthname " " year)
+           '(monthname " " day ", " year))))
+    (message "Julian date: %s"
+             (calendar-date-string
+              (calendar-julian-from-absolute
+               (calendar-absolute-from-gregorian
+                (or (calendar-cursor-to-date)
+                    (error "Cursor is not on a date!"))))))))
+
+(defun islamic-calendar-leap-year-p (year)
+  "Returns t if YEAR is a leap year on the Islamic calendar."
+  (memq (% year 30)
+        (list 2 5 7 10 13 16 18 21 24 26 29)))
+
+(defun islamic-calendar-last-day-of-month (month year)
+  "The last day in MONTH during YEAR on the Islamic calendar."
+  (cond
+   ((memq month (list 1 3 5 7 9 11)) 30)
+   ((memq month (list 2 4 6 8 10)) 29)
+   (t (if (islamic-calendar-leap-year-p year) 30 29))))
+
+(defun islamic-calendar-day-number (date)
+  "Return the day number within the year of the Islamic date DATE."
+    (let* ((month (extract-calendar-month date))
+           (day (extract-calendar-day date)))
+      (+ (* 30 (/ month 2))
+         (* 29 (/ (1- month) 2))
+         day)))
+
+(defun calendar-absolute-from-islamic (date)
+  "Absolute date of Islamic DATE.
+The absolute date is the number of days elapsed since the (imaginary)
+Gregorian date Sunday, December 31, 1 BC."
+  (let* ((month (extract-calendar-month date))
+         (day (extract-calendar-day date))
+         (year (extract-calendar-year date))
+         (y (% year 30))
+         (leap-years-in-cycle
+          (cond
+           ((< y 3) 0)  ((< y 6) 1)  ((< y 8) 2)  ((< y 11) 3) ((< y 14) 4)
+           ((< y 17) 5) ((< y 19) 6) ((< y 22) 7) ((< y 25) 8) ((< y 27) 9)
+           (t 10))))
+    (+ (islamic-calendar-day-number date);; days so far this year
+       (* (1- year) 354)                 ;; days in all non-leap years
+       (* 11 (/ year 30))                ;; leap days in complete cycles
+       leap-years-in-cycle               ;; leap days this cycle
+       227014)))                         ;; days before start of calendar
+
+(defun calendar-islamic-from-absolute (date)
+  "Compute the Islamic date (month day year) corresponding to absolute DATE.
+The absolute date is the number of days elapsed since the (imaginary)
+Gregorian date Sunday, December 31, 1 BC."
+  (if (< date 227015)
+      (list 0 0 0);; pre-Islamic date
+    (let* ((approx (/ (- date 227014) 355));; Approximation from below.
+           (year           ;; Search forward from the approximation.
+            (+ approx
+               (calendar-sum y approx
+                             (>= date (calendar-absolute-from-islamic
+                                       (list 1 1 (1+ y))))
+                             1)))
+           (month          ;; Search forward from Muharram.
+            (1+ (calendar-sum m 1
+                              (> date
+                                 (calendar-absolute-from-islamic
+                                  (list m
+                                        (islamic-calendar-last-day-of-month
+                                         m year)
+                                        year)))
+                              1)))
+           (day            ;; Calculate the day by subtraction.
+            (- date
+               (1- (calendar-absolute-from-islamic (list month 1 year))))))
+      (list month day year))))
+
+(defconst calendar-islamic-month-name-array
+  ["Muharram" "Safar" "Rabi I" "Rabi II" "Jumada I" "Jumada II"
+   "Rajab" "Sha'ban" "Ramadan" "Shawwal" "Dhu al-Qada" "Dhu al-Hijjah"])
+
+(defun cursor-to-islamic-calendar-date ()
+  "Show the Islamic calendar equivalent of the date under the cursor."
+  (interactive)
+  (let ((calendar-date-display-form
+           (if european-calendar-style
+               '(day " " monthname " " year)
+             '(monthname " " day ", " year)))
+        (calendar-month-name-array calendar-islamic-month-name-array)
+        (islamic-date (calendar-islamic-from-absolute
+                       (calendar-absolute-from-gregorian
+                        (or (calendar-cursor-to-date)
+                            (error "Cursor is not on a date!"))))))
+    (if (< (extract-calendar-year islamic-date) 1)
+        (message "Date is pre-Islamic")
+      (message "Islamic date: %s" (calendar-date-string islamic-date nil t)))))
+
+(defun calendar-hebrew-from-absolute (date)
+  "Compute the Hebrew date (month day year) corresponding to absolute DATE.
+The absolute date is the number of days elapsed since the (imaginary)
+Gregorian date Sunday, December 31, 1 BC."
+  (let* ((greg-date (calendar-gregorian-from-absolute date))
+         (month (aref [9 10 11 12 1 2 3 4 7 7 7 8]
+                 (1- (extract-calendar-month greg-date))))
+         (day)
+         (year (+ 3760 (extract-calendar-year greg-date))))
+    (while (>= date (calendar-absolute-from-hebrew (list 7 1 (1+ year))))
+        (setq year (1+ year)))
+    (let ((length (hebrew-calendar-last-month-of-year year)))
+      (while (> date
+                (calendar-absolute-from-hebrew
+                 (list month
+                       (hebrew-calendar-last-day-of-month month year)
+                       year)))
+        (setq month (1+ (% month length)))))
+    (setq day (1+
+               (- date (calendar-absolute-from-hebrew (list month 1 year)))))
+    (list month day year)))
+
+(defun hebrew-calendar-leap-year-p (year)
+  "t if YEAR is a Hebrew calendar leap year."
+  (< (% (1+ (* 7 year)) 19) 7))
+
+(defun hebrew-calendar-last-month-of-year (year)
+  "The last month of the Hebrew calendar YEAR."
+  (if (hebrew-calendar-leap-year-p year)
+      13
+    12))
+
+(defun hebrew-calendar-last-day-of-month (month year)
+  "The last day of MONTH in YEAR."
+  (if (or (memq month (list 2 4 6 10 13))
+          (and (= month 12) (not (hebrew-calendar-leap-year-p year)))
+          (and (= month 8) (not (hebrew-calendar-long-heshvan-p year)))
+          (and (= month 9) (hebrew-calendar-short-kislev-p year)))
+      29
+    30))
+
+(defun hebrew-calendar-elapsed-days (year)
+  "Number of days elapsed from the Sunday prior to the start of the Hebrew
+calendar to the mean conjunction of Tishri of Hebrew YEAR."
+  (let* ((months-elapsed
+          (+ (* 235 (/ (1- year) 19));; Months in complete cycles so far.
+             (* 12 (% (1- year) 19))      ;; Regular months in this cycle
+             (/ (1+ (* 7 (% (1- year) 19))) 19)));; Leap months this cycle
+         (parts-elapsed (+ 204 (* 793 (% months-elapsed 1080))))
+         (hours-elapsed (+ 5
+                           (* 12 months-elapsed)
+                           (* 793 (/ months-elapsed 1080))
+                           (/ parts-elapsed 1080)))
+         (parts                                  ;; Conjunction parts
+          (+ (* 1080 (% hours-elapsed 24)) (% parts-elapsed 1080)))
+         (day                                    ;; Conjunction day
+          (+ 1 (* 29 months-elapsed) (/ hours-elapsed 24)))
+         (alternative-day
+          (if (or (>= parts 19440)    ;; If the new moon is at or after midday,
+                  (and (= (% day 7) 2);; ...or is on a Tuesday...
+                       (>= parts 9924)  ;;    at 9 hours, 204 parts or later...
+                       (not (hebrew-calendar-leap-year-p year)));; of a
+                                                                ;; common year,
+                  (and (= (% day 7) 1);; ...or is on a Monday...
+                       (>= parts 16789) ;;   at 15 hours, 589 parts or later...
+                       (hebrew-calendar-leap-year-p (1- year))));; at the end
+                                                     ;; of a leap year
+       ;; Then postpone Rosh HaShanah one day
+              (1+ day)
+       ;; Else
+            day)))
+    (if ;; If Rosh HaShanah would occur on Sunday, Wednesday, or Friday
+        (memq (% alternative-day 7) (list 0 3 5))
+  ;; Then postpone it one (more) day and return        
+        (1+ alternative-day)
+  ;; Else return        
+      alternative-day)))
+
+(defun hebrew-calendar-days-in-year (year)
+  "Number of days in Hebrew YEAR."
+  (- (hebrew-calendar-elapsed-days (1+ year))
+     (hebrew-calendar-elapsed-days year)))
+
+(defun hebrew-calendar-long-heshvan-p (year)
+  "t if Heshvan is long in Hebrew YEAR."
+  (= (% (hebrew-calendar-days-in-year year) 10) 5))
+
+(defun hebrew-calendar-short-kislev-p (year)
+  "t if Kislev is short in Hebrew YEAR."
+  (= (% (hebrew-calendar-days-in-year year) 10) 3))
+
+(defun calendar-absolute-from-hebrew (date)
+  "Absolute date of Hebrew DATE.
+The absolute date is the number of days elapsed since the (imaginary)
+Gregorian date Sunday, December 31, 1 BC."
+  (let* ((month (extract-calendar-month date))
+         (day (extract-calendar-day date))
+         (year (extract-calendar-year date)))
+    (+ day                            ;; Days so far this month.
+       (if (< month 7);; before Tishri
+     ;; Then add days in prior months this year before and after Nisan
+           (+ (calendar-sum
+               m 7 (<= m (hebrew-calendar-last-month-of-year year))
+               (hebrew-calendar-last-day-of-month m year))
+              (calendar-sum
+               m 1 (< m month)
+               (hebrew-calendar-last-day-of-month m year)))
+     ;; Else add days in prior months this year
+         (calendar-sum
+          m 7 (< m month)
+          (hebrew-calendar-last-day-of-month m year)))
+    (hebrew-calendar-elapsed-days year);; Days in prior years.
+    -1373429)))                        ;; Days elapsed before absolute date 1.
+
+(defconst calendar-hebrew-month-name-array-common-year
+  ["Nisan" "Iyar" "Sivan" "Tammuz" "Av" "Elul" "Tishri"
+   "Heshvan" "Kislev" "Teveth" "Shevat" "Adar"])
+
+(defconst calendar-hebrew-month-name-array-leap-year
+  ["Nisan" "Iyar" "Sivan" "Tammuz" "Av" "Elul" "Tishri"
+   "Heshvan" "Kislev" "Teveth" "Shevat" "Adar I" "Adar II"])
+
+(defun cursor-to-hebrew-calendar-date ()
+  "Show the Hebrew calendar equivalent of the date under the cursor."
+  (interactive)
+  (let* ((calendar-date-display-form
+          (if european-calendar-style
+              '(day " " monthname " " year)
+            '(monthname " " day ", " year)))
+         (hebrew-date (calendar-hebrew-from-absolute
+                       (calendar-absolute-from-gregorian
+                        (or (calendar-cursor-to-date)
+                            (error "Cursor is not on a date!")))))
+         (calendar-month-name-array
+          (if (hebrew-calendar-leap-year-p (extract-calendar-year hebrew-date))
+              calendar-hebrew-month-name-array-leap-year
+            calendar-hebrew-month-name-array-common-year)))
+    (message "Hebrew date: %s" (calendar-date-string hebrew-date nil t))))
+
+(defun french-calendar-leap-year-p (year)
+  "True if YEAR is a leap year on the French Revolutionary calendar.
+For Gregorian years 1793 to 1805, the years of actual operation of the
+calendar, uses historical practice based on equinoxes is followed (years 3, 7,
+and 11 were leap years; 15 and 20 would have been leap years).  For later
+years uses the proposed rule of Romme (never adopted)--leap years fall every
+four years except century years not divisible 400 and century years that are
+multiples of 4000."
+  (or (memq year '(3 7 11));; Actual practice--based on equinoxes
+      (memq year '(15 20)) ;; Anticipated practice--based on equinoxes
+      (and (> year 20)     ;; Romme's proposal--never adopted
+           (zerop (% year 4))
+           (not (memq (% year 400) '(100 200 300)))
+           (not (zerop (% year 4000))))))
+
+(defun french-calendar-last-day-of-month (month year)
+  "Last day of MONTH, YEAR on the French Revolutionary calendar.
+The 13th month is not really a month, but the 5 (6 in leap years) day period of
+`sansculottides' at the end of the year."
+  (if (< month 13)
+      30
+    (if (french-calendar-leap-year-p year)
+        6
+      5)))
+
+(defun calendar-absolute-from-french (date)
+  "Absolute date of French Revolutionary DATE.
+The absolute date is the number of days elapsed since the (imaginary)
+Gregorian date Sunday, December 31, 1 BC."
+  (let ((month (extract-calendar-month date))
+        (day (extract-calendar-day date))
+        (year (extract-calendar-year date)))
+    (+ (* 365 (1- year));; Days in prior years
+       ;; Leap days in prior years
+       (if (< year 20)
+           (/ year 4);; Actual and anticipated practice (years 3, 7, 11, 15)
+         ;; Romme's proposed rule (using the Principle of Inclusion/Exclusion)
+         (+ (/ (1- year) 4);; Luckily, there were 4 leap years before year 20
+            (- (/ (1- year) 100))
+            (/ (1- year) 400)
+            (- (/ (1- year) 4000))))
+       (* 30 (1- month));; Days in prior months this year
+       day;; Days so far this month
+       654414)));; Days before start of calendar (September 22, 1792).
+
+(defun calendar-french-from-absolute (date)
+  "Compute the French Revolutionary date (month day year) corresponding to
+absolute DATE.  The absolute date is the number of days elapsed since the
+(imaginary) Gregorian date Sunday, December 31, 1 BC."
+  (if (< date 654415)
+      (list 0 0 0);; pre-French Revolutionary date
+    (let* ((approx (/ (- date 654414) 366));; Approximation from below.
+           (year                ;; Search forward from the approximation.
+            (+ approx
+               (calendar-sum y approx
+                 (>= date (calendar-absolute-from-french (list 1 1 (1+ y))))
+                 1)))
+           (month               ;; Search forward from Vendemiaire.
+            (1+ (calendar-sum m 1
+                  (> date
+                     (calendar-absolute-from-french
+                      (list m
+                            (french-calendar-last-day-of-month m year)
+                            year)))
+                  1)))
+           (day                   ;; Calculate the day by subtraction.
+            (- date
+               (1- (calendar-absolute-from-french (list month 1 year))))))
+    (list month day year))))
+
+(defun cursor-to-french-calendar-date ()
+  "Show the French Revolutionary calendar equivalent of the date under the
+cursor."
+  (interactive)
+  (let* ((french-date (calendar-french-from-absolute
+                       (calendar-absolute-from-gregorian
+                        (or (calendar-cursor-to-date)
+                            (error "Cursor is not on a date!")))))
+         (y (extract-calendar-year french-date))
+         (m (extract-calendar-month french-date))
+         (d (extract-calendar-day french-date)))
+    (if (< y 1)
+        (message "Date is pre-French Revolution")
+      (if (= m 13)
+          (message "Jour %s de l'Annee %d de la Revolution"
+                   (aref french-calendar-special-days-array (1- d))
+                   y)
+        (message "Decade %s, %s de %s de l'Annee %d de la Revolution"
+                 (make-string (1+ (/ (1- d) 10)) ?I)
+                 (aref french-calendar-day-name-array (% (1- d) 10))
+                 (aref french-calendar-month-name-array (1- m))
+                 y)))))
+
+(defconst french-calendar-month-name-array
+  ["Vendemiaire" "Brumaire" "Frimaire" "Nivose" "Pluviose" "Ventose" "Germinal"
+   "Floreal" "Prairial" "Messidor" "Thermidor" "Fructidor"])
+;; Very loosely translated as
+;; Slippy, Nippy, Drippy, Freezy, Wheezy, Sneezy,
+;; Showery, Flowery, Bowery, Heaty, Wheaty, Sweety.
+
+(defconst french-calendar-day-name-array
+  ["Primidi" "Duodi" "Tridi" "Quartidi" "Quintidi" "Sextidi" "Septidi"
+   "Octidi" "Nonidi" "Decadi"])
+
+(defconst french-calendar-special-days-array
+  ["de la Vertu" "du Genie" "du Labour" "de la Raison" "de la Recompense"
+   "de la Revolution"])
+
+(provide 'calendar)
+