39. Customizing the Calendar and Diary

There are many customizations that you can use to make the calendar and diary suit your personal tastes.

39.1 Customizing the Calendar

If you set the variable view-diary-entries-initially to t, calling up the calendar automatically displays the diary entries for the current date as well. The diary dates appear only if the current date is visible. If you add both of the following lines to your init file:

(setq view-diary-entries-initially t)
(calendar)

this displays both the calendar and diary windows whenever you start Emacs.

Similarly, if you set the variable view-calendar-holidays-initially to t, entering the calendar automatically displays a list of holidays for the current three-month period. The holiday list appears in a separate window.

You can set the variable mark-diary-entries-in-calendar to t in order to mark any dates with diary entries. This takes effect whenever the calendar window contents are recomputed. There are two ways of marking these dates: by changing the face (see section 38.11 Faces), or by placing a plus sign (`+') beside the date.

Similarly, setting the variable mark-holidays-in-calendar to t marks holiday dates, either with a change of face or with an asterisk (`*').

The variable calendar-holiday-marker specifies how to mark a date as being a holiday. Its value may be a character to insert next to the date, or a face name to use for displaying the date. Likewise, the variable diary-entry-marker specifies how to mark a date that has diary entries. The calendar creates faces named holiday-face and diary-face for these purposes; those symbols are the default values of these variables.

The variable calendar-load-hook is a normal hook run when the calendar package is first loaded (before actually starting to display the calendar).

Starting the calendar runs the normal hook initial-calendar-window-hook. Recomputation of the calendar display does not run this hook. But if you leave the calendar with the q command and reenter it, the hook runs again.

The variable today-visible-calendar-hook is a normal hook run after the calendar buffer has been prepared with the calendar when the current date is visible in the window. One use of this hook is to replace today's date with asterisks; to do that, use the hook function calendar-star-date.

(add-hook 'today-visible-calendar-hook 'calendar-star-date)

Another standard hook function marks the current date, either by changing its face or by adding an asterisk. Here's how to use it:

(add-hook 'today-visible-calendar-hook 'calendar-mark-today)

The variable calendar-today-marker specifies how to mark today's date. Its value should be a character to insert next to the date or a face name to use for displaying the date. A face named calendar-today-face is provided for this purpose; that symbol is the default for this variable.

A similar normal hook, today-invisible-calendar-hook is run if the current date is not visible in the window.

Starting in Emacs 21, each of the calendar cursor motion commands runs the hook calendar-move-hook after it moves the cursor.

39.2 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.

(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.

(holiday-hebrew month day string)

A fixed date on the Hebrew calendar.

(holiday-islamic month day string)

A fixed date on the Islamic calendar.

(holiday-julian month day string)

A fixed date on the Julian calendar.

(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).

(if condition 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 as follows:

(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") ... )

39.3 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))

39.4 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 ")"))

39.5 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, which is the center of GNU's world.

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 start and end dates of daylight savings time as holidays 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)

i.e., 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 is 60.

The variable calendar-daylight-savings-starts-time and the variable 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, both variables' values are 120.

39.6 Customizing the Diary

Ordinarily, the mode line of the diary buffer window indicates any holidays that fall on the date of the diary entries. The process of checking for holidays can take several seconds, so including holiday information delays the display of the diary buffer noticeably. If you'd prefer to have a faster display of the diary buffer but without the holiday information, set the variable holidays-in-diary-buffer to nil.

The variable number-of-diary-entries controls the number of days of diary entries to be displayed at one time. It affects the initial display when view-diary-entries-initially is t, as well as the command M-x diary. For example, the default value is 1, which says to display only the current day's diary entries. If the value is 2, both the current day's and the next day's entries are displayed. The value can also be a vector of seven elements: for example, if the value is [0 2 2 2 2 4 1] then no diary entries appear on Sunday, the current date's and the next day's diary entries appear Monday through Thursday, Friday through Monday's entries appear on Friday, while on Saturday only that day's entries appear.

The variable print-diary-entries-hook is a normal hook run after preparation of a temporary buffer containing just the diary entries currently visible in the diary buffer. (The other, irrelevant diary entries are really absent from the temporary buffer; in the diary buffer, they are merely hidden.) The default value of this hook does the printing with the command lpr-buffer. If you want to use a different command to do the printing, just change the value of this hook. Other uses might include, for example, rearranging the lines into order by day and time.

You can customize the form of dates in your diary file, if neither the standard American nor European styles suits your needs, by setting the variable diary-date-forms. This variable is a list of patterns for recognizing a date. Each date pattern is a list whose elements may be regular expressions (see section 34.2 Regular Expressions) or the symbols month, day, year, monthname, and dayname. All these elements serve as patterns that match certain kinds of text in the diary file. In order for the date pattern, as a whole, to match, all of its elements must match consecutively.

A regular expression in a date pattern matches in its usual fashion, using the standard syntax table altered so that `*' is a word constituent.

The symbols month, day, year, monthname, and dayname match the month number, day number, year number, month name, and day name of the date being considered. The symbols that match numbers allow leading zeros; those that match names allow three-letter abbreviations and capitalization. All the symbols can match `*'; since `*' in a diary entry means "any day", "any month", and so on, it should match regardless of the date being considered.

The default value of diary-date-forms in the American style is this:

((month "/" day "[^/0-9]")
 (month "/" day "/" year "[^0-9]")
 (monthname " *" day "[^,0-9]")
 (monthname " *" day ", *" year "[^0-9]")
 (dayname "\\W"))

The date patterns in the list must be mutually exclusive and must not match any portion of the diary entry itself, just the date and one character of whitespace. If, to be mutually exclusive, the pattern must match a portion of the diary entry text--beyond the whitespace that ends the date--then the first element of the date pattern must be backup. This causes the date recognizer to back up to the beginning of the current word of the diary entry, after finishing the match. Even if you use backup, the date pattern must absolutely not match more than a portion of the first word of the diary entry. The default value of diary-date-forms in the European style is this list:

((day "/" month "[^/0-9]")
 (day "/" month "/" year "[^0-9]")
 (backup day " *" monthname "\\W+\\<[^*0-9]")
 (day " *" monthname " *" year "[^0-9]")
 (dayname "\\W"))

Notice the use of backup in the third pattern, because it needs to match part of a word beyond the date itself to distinguish it from the fourth pattern.

39.7 Hebrew- and Islamic-Date Diary Entries

Your diary file can have entries based on Hebrew or Islamic dates, as well as entries based on the world-standard Gregorian calendar. However, because recognition of such entries is time-consuming and most people don't use them, you must explicitly enable their use. If you want the diary to recognize Hebrew-date diary entries, for example, you must do this:

(add-hook 'nongregorian-diary-listing-hook 'list-hebrew-diary-entries)
(add-hook 'nongregorian-diary-marking-hook 'mark-hebrew-diary-entries)

If you want Islamic-date entries, do this:

(add-hook 'nongregorian-diary-listing-hook 'list-islamic-diary-entries)
(add-hook 'nongregorian-diary-marking-hook 'mark-islamic-diary-entries)

Hebrew- and Islamic-date diary entries have the same formats as Gregorian-date diary entries, except that `H' precedes a Hebrew date and `I' precedes an Islamic date. Moreover, because the Hebrew and Islamic month names are not uniquely specified by the first three letters, you may not abbreviate them. For example, a diary entry for the Hebrew date Heshvan 25 could look like this:

HHeshvan 25 Happy Hebrew birthday!

and would appear in the diary for any date that corresponds to Heshvan 25 on the Hebrew calendar. And here is an Islamic-date diary entry that matches Dhu al-Qada 25:

IDhu al-Qada 25 Happy Islamic birthday!

As with Gregorian-date diary entries, Hebrew- and Islamic-date entries are nonmarking if they are preceded with an ampersand (`&').

Here is a table of commands used in the calendar to create diary entries that match the selected date and other dates that are similar in the Hebrew or Islamic calendar:

i h d

Add a diary entry for the Hebrew date corresponding to the selected date (insert-hebrew-diary-entry).

i h m

Add a diary entry for the day of the Hebrew month corresponding to the selected date (insert-monthly-hebrew-diary-entry). This diary entry matches any date that has the same Hebrew day-within-month as the selected date.

i h y

Add a diary entry for the day of the Hebrew year corresponding to the selected date (insert-yearly-hebrew-diary-entry). This diary entry matches any date which has the same Hebrew month and day-within-month as the selected date.

i i d

Add a diary entry for the Islamic date corresponding to the selected date (insert-islamic-diary-entry).

i i m

Add a diary entry for the day of the Islamic month corresponding to the selected date (insert-monthly-islamic-diary-entry).

i i y

Add a diary entry for the day of the Islamic year corresponding to the selected date (insert-yearly-islamic-diary-entry).

These commands work much like the corresponding commands for ordinary diary entries: they apply to the date that point is on in the calendar window, and what they do is insert just the date portion of a diary entry at the end of your diary file. You must then insert the rest of the diary entry.

39.8 Fancy Diary Display

Diary display works by preparing the diary buffer and then running the hook diary-display-hook. The default value of this hook (simple-diary-display) hides the irrelevant diary entries and then displays the buffer. However, if you specify the hook as follows,

(add-hook 'diary-display-hook 'fancy-diary-display)

this enables fancy diary display. It displays diary entries and holidays by copying them into a special buffer that exists only for the sake of display. Copying to a separate buffer provides an opportunity to change the displayed text to make it prettier--for example, to sort the entries by the dates they apply to.

As with simple diary display, you can print a hard copy of the buffer with print-diary-entries. To print a hard copy of a day-by-day diary for a week, position point on Sunday of that week, type 7 d, and then do M-x print-diary-entries. As usual, the inclusion of the holidays slows down the display slightly; you can speed things up by setting the variable holidays-in-diary-buffer to nil.

Ordinarily, the fancy diary buffer does 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.

If you use the fancy diary display, you can use the normal hook list-diary-entries-hook to sort each day's diary entries by their time of day. Here's how:

(add-hook 'list-diary-entries-hook 'sort-diary-entries t)

For each day, this sorts diary entries that begin with a recognizable time of day according to their times. Diary entries without times come first within each day.

Fancy diary display also has the ability to process included diary files. This permits a group of people to share a diary file for events that apply to all of them. Lines in the diary file of this form:

#include "filename"

includes the diary entries from the file filename in the fancy diary buffer. The include mechanism is recursive, so that included files can include other files, and so on; you must be careful not to have a cycle of inclusions, of course. Here is how to enable the include facility:

(add-hook 'list-diary-entries-hook 'include-other-diary-files)
(add-hook 'mark-diary-entries-hook 'mark-included-diary-files)

The include mechanism works only with the fancy diary display, because ordinary diary display shows the entries directly from your diary file.

39.9 Sexp Entries and the Fancy Diary Display

Sexp diary entries allow you to do more than just have complicated conditions under which a diary entry applies. If you use the fancy diary display, sexp entries can generate the text of the entry depending on the date itself. For example, an anniversary diary entry can insert the number of years since the anniversary date into the text of the diary entry. Thus the `%d' in this dairy entry:

%%(diary-anniversary 10 31 1948) Arthur's birthday (%d years old)

gets replaced by the age, so on October 31, 1990 the entry appears in the fancy diary buffer like this:

Arthur's birthday (42 years old)

If the diary file instead contains this entry:

%%(diary-anniversary 10 31 1948) Arthur's %d%s birthday

the entry in the fancy diary buffer for October 31, 1990 appears like this:

Arthur's 42nd birthday

Similarly, cyclic diary entries can interpolate the number of repetitions that have occurred:

%%(diary-cyclic 50 1 1 1990) Renew medication (%d%s time)

looks like this:

Renew medication (5th time)

in the fancy diary display on September 8, 1990.

There is an early reminder diary sexp that includes its entry in the diary not only on the date of occurrence, but also on earlier dates. For example, if you want a reminder a week before your anniversary, you can use

%%(diary-remind '(diary-anniversary 12 22 1968) 7) Ed's anniversary

and the fancy diary will show

Ed's anniversary

The function diary-date applies to dates described by a month, day, year combination, each of which can be an integer, a list of integers, or t. The value t means all values. For example,

%%(diary-date '(10 11 12) 22 t) Rake leaves

causes the fancy diary to show

Rake leaves

on October 22, November 22, and December 22 of every year.

The function diary-float allows you to describe diary entries that apply to dates like the third Friday of November, or the last Tuesday in April. The parameters are the month, dayname, and an index n. The entry appears on the nth dayname of month, where dayname=0 means Sunday, 1 means Monday, and so on. If n is negative it counts backward from the end of month. The value of month can be a list of months, a single month, or t to specify all months. You can also use an optional parameter day to specify the nth dayname of month on or after/before day; the value of day defaults to 1 if n is positive and to the last day of month if n is negative. For example,

%%(diary-float t 1 -1) Pay rent

causes the fancy diary to show

Pay rent

on the last Monday of every month.

The generality of sexp diary entries lets you specify any diary entry that you can describe algorithmically. A sexp diary entry contains an expression that computes whether the entry applies to any given date. If its value is non-nil, the entry applies to that date; otherwise, it does not. The expression can use the variable date to find the date being considered; its value is a list (month day year) that refers to the Gregorian calendar.

Suppose you get paid on the 21st of the month if it is a weekday, and on the Friday before if the 21st is on a weekend. Here is how to write a sexp diary entry that matches those dates:

&%%(let ((dayname (calendar-day-of-week date))
         (day (car (cdr date))))
      (or (and (= day 21) (memq dayname '(1 2 3 4 5)))
          (and (memq day '(19 20)) (= dayname 5)))
         ) Pay check deposited

The following sexp diary entries take advantage of the ability (in the fancy diary display) to concoct diary entries whose text varies based on the date:

%%(diary-sunrise-sunset)

Make a diary entry for the local times of today's sunrise and sunset.

%%(diary-phases-of-moon)

Make a diary entry for the phases (quarters) of the moon.

%%(diary-day-of-year)

Make a diary entry with today's day number in the current year and the number of days remaining in the current year.

%%(diary-iso-date)

Make a diary entry with today's equivalent ISO commercial date.

%%(diary-julian-date)

Make a diary entry with today's equivalent date on the Julian calendar.

%%(diary-astro-day-number)

Make a diary entry with today's equivalent astronomical (Julian) day number.

%%(diary-hebrew-date)

Make a diary entry with today's equivalent date on the Hebrew calendar.

%%(diary-islamic-date)

Make a diary entry with today's equivalent date on the Islamic calendar.

%%(diary-french-date)

Make a diary entry with today's equivalent date on the French Revolutionary calendar.

%%(diary-mayan-date)

Make a diary entry with today's equivalent date on the Mayan calendar.

Thus including the diary entry

&%%(diary-hebrew-date)

causes every day's diary display to contain the equivalent date on the Hebrew calendar, if you are using the fancy diary display. (With simple diary display, the line `&%%(diary-hebrew-date)' appears in the diary for any date, but does nothing particularly useful.)

These functions can be used to construct sexp diary entries based on the Hebrew calendar in certain standard ways:

%%(diary-rosh-hodesh)

Make a diary entry that tells the occurrence and ritual announcement of each new Hebrew month.

%%(diary-parasha)

Make a Saturday diary entry that tells the weekly synagogue scripture reading.

%%(diary-sabbath-candles)

Make a Friday diary entry that tells the local time of Sabbath candle lighting.

%%(diary-omer)

Make a diary entry that gives the omer count, when appropriate.

%%(diary-yahrzeit month day year) name

Make a diary entry marking the anniversary of a date of death. The date is the Gregorian (civil) date of death. The diary entry appears on the proper Hebrew calendar anniversary and on the day before. (In the European style, the order of the parameters is changed to day, month, year.)

39.10 Customizing Appointment Reminders

You can specify exactly how Emacs reminds you of an appointment, and how far in advance it begins doing so, by setting these variables:

appt-message-warning-time

The time in minutes before an appointment that the reminder begins. The default is 10 minutes.

appt-audible

If this is non-nil, Emacs rings the terminal bell for appointment reminders. The default is t.

appt-visible

If this is non-nil, Emacs displays the appointment message in the echo area. The default is t.

appt-display-mode-line

If this is non-nil, Emacs displays the number of minutes to the appointment on the mode line. The default is t.

appt-msg-window

If this is non-nil, Emacs displays the appointment message in another window. The default is t.

appt-disp-window-function

This variable holds a function to use to create the other window for the appointment message.

appt-delete-window-function

This variable holds a function to use to get rid of the appointment message window, when its time is up.

appt-display-duration

The number of seconds to display an appointment message. The default is 5 seconds.