-\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 init file:
-
- (setq other-holidays '((holiday-fixed 7 14 "Bastille Day")))
-
- *Note Init File::.
-
-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") ... )
-
-\1f
-File: xemacs.info, Node: Date Display Format, Next: Time Display Format, Prev: Holiday Customizing, Up: Calendar Customization
-
-Date Display Format
-...................
-
- You can customize the manner of displaying dates in the diary, in
-mode lines, and in messages by setting `calendar-date-display-form'.
-This variable holds a list of expressions that can involve the variables
-`month', `day', and `year', which are all numbers in string form, and
-`monthname' and `dayname', which are both alphabetic strings. In the
-American style, the default value of this list is as follows:
-
- ((if dayname (concat dayname ", ")) monthname " " day ", " year)
-
-while in the European style this value is the default:
-
- ((if dayname (concat dayname ", ")) day " " monthname " " year)
-
- + The ISO standard date representation is this:
-
- (year "-" month "-" day)
-
-This specifies a typical American format:
-
- (month "/" day "/" (substring year -2))
-
-\1f
-File: xemacs.info, Node: Time Display Format, Next: Daylight Savings, Prev: Date Display Format, Up: Calendar Customization
-
-Time Display Format
-...................
-
- The calendar and diary by default display times of day in the
-conventional American style with the hours from 1 through 12, minutes,
-and either `am' or `pm'. If you prefer the European style, also known
-in the US as military, in which the hours go from 00 to 23, you can
-alter the variable `calendar-time-display-form'. This variable is a
-list of expressions that can involve the variables `12-hours',
-`24-hours', and `minutes', which are all numbers in string form, and
-`am-pm' and `time-zone', which are both alphabetic strings. The
-default value of `calendar-time-display-form' is as follows:
-
- (12-hours ":" minutes am-pm
- (if time-zone " (") time-zone (if time-zone ")"))
-
-Here is a value that provides European style times:
-
- (24-hours ":" minutes
- (if time-zone " (") time-zone (if time-zone ")"))
-
-gives military-style times like `21:07 (UT)' if time zone names are
-defined, and times like `21:07' if they are not.
-
-\1f
-File: xemacs.info, Node: Daylight Savings, Next: Diary Customizing, Prev: Time Display Format, Up: Calendar Customization
-
-Daylight Savings Time
-.....................
-
- Emacs understands the difference between standard time and daylight
-savings time--the times given for sunrise, sunset, solstices,
-equinoxes, and the phases of the moon take that into account. The rules
-for daylight savings time vary from place to place and have also varied
-historically from year to year. To do the job properly, Emacs needs to
-know which rules to use.
-
- Some operating systems keep track of the rules that apply to the
-place where you are; on these systems, Emacs gets the information it
-needs from the system automatically. If some or all of this
-information is missing, Emacs fills in the gaps with the rules
-currently used in Cambridge, Massachusetts. If the resulting rules are
-not what you want, you can tell Emacs the rules to use by setting
-certain variables.
-
- If the default choice of rules is not appropriate for your location,
-you can tell Emacs the rules to use by setting the variables
-`calendar-daylight-savings-starts' and
-`calendar-daylight-savings-ends'. Their values should be Lisp
-expressions that refer to the variable `year', and evaluate to the
-Gregorian date on which daylight savings time starts or (respectively)
-ends, in the form of a list `(MONTH DAY YEAR)'. The values should be
-`nil' if your area does not use daylight savings time.
-
- Emacs uses these expressions to determine the starting date of
-daylight savings time for the holiday list and for correcting times of
-day in the solar and lunar calculations.
-
- The values for Cambridge, Massachusetts are as follows:
-
- (calendar-nth-named-day 1 0 4 year)
- (calendar-nth-named-day -1 0 10 year)
-
-That is, the first 0th day (Sunday) of the fourth month (April) in the
-year specified by `year', and the last Sunday of the tenth month
-(October) of that year. If daylight savings time were changed to start
-on October 1, you would set `calendar-daylight-savings-starts' to this:
-
- (list 10 1 year)
-
- For a more complex example, suppose daylight savings time begins on
-the first of Nisan on the Hebrew calendar. You should set
-`calendar-daylight-savings-starts' to this value:
-
- (calendar-gregorian-from-absolute
- (calendar-absolute-from-hebrew
- (list 1 1 (+ year 3760))))
-
-because Nisan is the first month in the Hebrew calendar and the Hebrew
-year differs from the Gregorian year by 3760 at Nisan.
-
- If there is no daylight savings time at your location, or if you want
-all times in standard time, set `calendar-daylight-savings-starts' and
-`calendar-daylight-savings-ends' to `nil'.
-
- The variable `calendar-daylight-time-offset' specifies the
-difference between daylight savings time and standard time, measured in
-minutes. The value for Cambridge, Massachusetts is 60.
-
- The two variables `calendar-daylight-savings-starts-time' and
-`calendar-daylight-savings-ends-time' specify the number of minutes
-after midnight local time when the transition to and from daylight
-savings time should occur. For Cambridge, Massachusetts both variables'
-values are 120.
-