-\1f
-File: xemacs.info, Node: Holiday Customizing, Next: Date Display Format, Prev: Calendar Customizing, Up: Calendar Customization
-
-Customizing the Holidays
-........................
-
- Emacs knows about holidays defined by entries on one of several
-lists. You can customize these lists of holidays to your own needs,
-adding or deleting holidays. The lists of holidays that Emacs uses are
-for general holidays (`general-holidays'), local holidays
-(`local-holidays'), Christian holidays (`christian-holidays'), Hebrew
-(Jewish) holidays (`hebrew-holidays'), Islamic (Moslem) holidays
-(`islamic-holidays'), and other holidays (`other-holidays').
-
- The general holidays are, by default, holidays common throughout the
-United States. To eliminate these holidays, set `general-holidays' to
-`nil'.
-
- There are no default local holidays (but sites may supply some). You
-can set the variable `local-holidays' to any list of holidays, as
-described below.
-
- By default, Emacs does not include all the holidays of the religions
-that it knows, only those commonly found in secular calendars. For a
-more extensive collection of religious holidays, you can set any (or
-all) of the variables `all-christian-calendar-holidays',
-`all-hebrew-calendar-holidays', or `all-islamic-calendar-holidays' to
-`t'. If you want to eliminate the religious holidays, set any or all
-of the corresponding variables `christian-holidays', `hebrew-holidays',
-and `islamic-holidays' to `nil'.
-
- You can set the variable `other-holidays' to any list of holidays.
-This list, normally empty, is intended for individual use.
-
- Each of the lists (`general-holidays', `local-holidays',
-`christian-holidays', `hebrew-holidays', `islamic-holidays', and
-`other-holidays') is a list of "holiday forms", each holiday form
-describing a holiday (or sometimes a list of holidays).
-
- Here is a table of the possible kinds of holiday form. Day numbers
-and month numbers count starting from 1, but "dayname" numbers count
-Sunday as 0. The element STRING is always the name of the holiday, as
-a string.
-
-`(holiday-fixed MONTH DAY STRING)'
- A fixed date on the Gregorian calendar. MONTH and DAY are
- numbers, STRING is the name of the holiday.
-
-`(holiday-float MONTH DAYNAME K STRING)'
- The Kth DAYNAME in MONTH on the Gregorian calendar (DAYNAME=0 for
- Sunday, and so on); negative K means count back from the end of
- the month. STRING is the name of the holiday.
-
-`(holiday-hebrew MONTH DAY STRING)'
- A fixed date on the Hebrew calendar. MONTH and DAY are numbers,
- STRING is the name of the holiday.
-
-`(holiday-islamic MONTH DAY STRING)'
- A fixed date on the Islamic calendar. MONTH and DAY are numbers,
- STRING is the name of the holiday.
-
-`(holiday-julian MONTH DAY STRING)'
- A fixed date on the Julian calendar. MONTH and DAY are numbers,
- STRING is the name of the holiday.
-
-`(holiday-sexp SEXP STRING)'
- A date calculated by the Lisp expression SEXP. The expression
- should use the variable `year' to compute and return the date of a
- holiday, or `nil' if the holiday doesn't happen this year. The
- value of SEXP must represent the date as a list of the form
- `(MONTH DAY YEAR)'. STRING is the name of the holiday.
-
-`(if CONDITION HOLIDAY-FORM &optional HOLIDAY-FORM)'
- A holiday that happens only if CONDITION is true.
-
-`(FUNCTION [ARGS])'
- A list of dates calculated by the function FUNCTION, called with
- arguments ARGS.
-
- For example, suppose you want to add Bastille Day, celebrated in
-France on July 14. You can do this by adding the following line to
-your `.emacs' file:
-
- (setq other-holidays '((holiday-fixed 7 14 "Bastille Day")))
-
-The holiday form `(holiday-fixed 7 14 "Bastille Day")' specifies the
-fourteenth day of the seventh month (July).
-
- Many holidays occur on a specific day of the week, at a specific time
-of month. Here is a holiday form describing Hurricane Supplication Day,
-celebrated in the Virgin Islands on the fourth Monday in August:
-
- (holiday-float 8 1 4 "Hurricane Supplication Day")
-
-Here the 8 specifies August, the 1 specifies Monday (Sunday is 0,
-Tuesday is 2, and so on), and the 4 specifies the fourth occurrence in
-the month (1 specifies the first occurrence, 2 the second occurrence,
--1 the last occurrence, -2 the second-to-last occurrence, and so on).
-
- You can specify holidays that occur on fixed days of the Hebrew,
-Islamic, and Julian calendars too. For example,
-
- (setq other-holidays
- '((holiday-hebrew 10 2 "Last day of Hanukkah")
- (holiday-islamic 3 12 "Mohammed's Birthday")
- (holiday-julian 4 2 "Jefferson's Birthday")))
-
-adds the last day of Hanukkah (since the Hebrew months are numbered with
-1 starting from Nisan), the Islamic feast celebrating Mohammed's
-birthday (since the Islamic months are numbered from 1 starting with
-Muharram), and Thomas Jefferson's birthday, which is 2 April 1743 on the
-Julian calendar.
-
- To include a holiday conditionally, use either Emacs Lisp's `if' or
-the `holiday-sexp' form. For example, American presidential elections
-occur on the first Tuesday after the first Monday in November of years
-divisible by 4:
-
- (holiday-sexp (if (= 0 (% year 4))
- (calendar-gregorian-from-absolute
- (1+ (calendar-dayname-on-or-before
- 1 (+ 6 (calendar-absolute-from-gregorian
- (list 11 1 year))))))
- "US Presidential Election"))
-
-or
-
- (if (= 0 (% 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"))
-
- Some holidays just don't fit into any of these forms because special
-calculations are involved in their determination. In such cases you
-must write a Lisp function to do the calculation. To include eclipses,
-for example, add `(eclipses)' to `other-holidays' and write an Emacs
-Lisp function `eclipses' that returns a (possibly empty) list of the
-relevant Gregorian dates among the range visible in the calendar
-window, with descriptive strings, like this:
-
- (((6 27 1991) "Lunar Eclipse") ((7 11 1991) "Solar Eclipse") ... )