Calendar Mode and the Diary
===========================

Emacs provides the functions of a desk calendar, with a diary of planned or past events.  To enter the calendar, type M-x calendar; this displays a three-month calendar centered on the current month, with point on the current date.  With a numeric argument, as in C-u M-x calendar, it prompts you for the month and year to be the center of the three-month calendar.  The calendar uses its own buffer, whose major mode is Calendar mode.

Button2 in the calendar brings up a menu of operations on a particular date; Buttons3 brings up a menu of commonly used calendar features that are independent of any particular date.  To exit the calendar, type q.  See Customizing the Calendar and Diary (The XEmacs Lisp Reference Manual), for customization information about the calendar and diary.

Movement in the Calendar
------------------------

Calendar mode lets you move through the calendar in logical units of time such as days, weeks, months, and years.  If you move outside the three months originally displayed, the calendar display ``scrolls'' automatically through time to make the selected date visible.  Moving to a date lets you view its holidays or diary entries, or convert it to other calendars; moving longer time periods is also useful simply to scroll the calendar.

Motion by Integral Days, Weeks, Months, Years
.............................................

The commands for movement in the calendar buffer parallel the commands for movement in text.  You can move forward and backward by days, weeks, months, and years.

C-f
     Move point one day forward (calendar-forward-day).

C-b
     Move point one day backward (calendar-backward-day).

C-n
     Move point one week forward (calendar-forward-week).

C-p
     Move point one week backward (calendar-backward-week).

M-}
     Move point one month forward (calendar-forward-month).

M-{
     Move point one month backward (calendar-backward-month).

C-x ]
     Move point one year forward (calendar-forward-year).

C-x [
     Move point one year backward (calendar-backward-year).

The day and week commands are natural analogues of the usual Emacs commands for moving by characters and by lines.  Just as C-n usually moves to the same column in the following line, in Calendar mode it moves to the same day in the following week.  And C-p moves to the same day in the previous week.

The arrow keys are equivalent to C-f, C-b, C-n and C-p, just as they normally are in other modes.

The commands for motion by months and years work like those for weeks, but move a larger distance.  The month commands M-} and M-{ move forward or backward by an entire month's time.  The year commands C-x ] and C-x [ move forward or backward a whole year.

The easiest way to remember these commands is to consider months and years analogous to paragraphs and pages of text, respectively.  But the commands themselves are not quite analogous.  The ordinary Emacs paragraph commands move to the beginning or end of a paragraph, whereas these month and year commands move by an entire month or an entire year, which usually involves skipping across the end of a month or year.

All these commands accept a numeric argument as a repeat count. For convenience, the digit keys and the minus sign specify numeric arguments in Calendar mode even without the Meta modifier.  For example, 100 C-f moves point 100 days forward from its present location.

Beginning or End of Week, Month or Year
.......................................

A week (or month, or year) is not just a quantity of days; we think of weeks (months, years) as starting on particular dates.  So Calendar mode provides commands to move to the beginning or end of a week, month or year:

C-a
     Move point to start of week (calendar-beginning-of-week).

C-e
     Move point to end of week (calendar-end-of-week).

M-a
     Move point to start of month (calendar-beginning-of-month).

M-e
     Move point to end of month (calendar-end-of-month).

M-<
     Move point to start of year (calendar-beginning-of-year).

M->
     Move point to end of year (calendar-end-of-year).

These commands also take numeric arguments as repeat counts, with the repeat count indicating how many weeks, months, or years to move backward or forward.

By default, weeks begin on Sunday.  To make them begin on Monday instead, set the variable calendar-week-start-day to 1.

Particular Dates
................

Calendar mode provides commands for moving to a particular date specified in various ways.

g d
     Move point to specified date (calendar-goto-date).

o
     Center calendar around specified month (calendar-other-month).

.
     Move point to today's date (calendar-goto-today).

g d (calendar-goto-date) prompts for a year, a month, and a day of the month, and then moves to that date.  Because the calendar includes all dates from the beginning of the current era, you must type the year in its entirety; that is, type 1990, not 90.

o (calendar-other-month) prompts for a month and year, then centers the three-month calendar around that month.

You can return to today's date with . (calendar-goto-today).

Scrolling the Calendar through Time
-----------------------------------

The calendar display scrolls automatically through time when you move out of the visible portion.  You can also scroll it manually.  Imagine that the calendar window contains a long strip of paper with the months on it. Scrolling it means moving the strip so that new months become visible in the window.

C-x <
     Scroll calendar one month forward (scroll-calendar-left).

C-x >
     Scroll calendar one month backward (scroll-calendar-right).

C-v
NEXT
     Scroll calendar three months forward (scroll-calendar-left-three-months).

M-v
PRIOR
     Scroll calendar three months backward (scroll-calendar-right-three-months).

The most basic calendar scroll commands scroll by one month at a time.  This means that there are two months of overlap between the display before the command and the display after.  C-x < scrolls the calendar contents one month to the left; that is, it moves the display forward in time.  C-x > scrolls the contents to the right, which moves backwards in time.

The commands C-v and M-v scroll the calendar by an entire ``screenful''---three months---in analogy with the usual meaning of these commands.  C-v makes later dates visible and M-v makes earlier dates visible.  These commands take a numeric argument as a repeat count; in particular, since C-u multiplies the next command by four, typing C-u C-v scrolls the calendar forward by a year and typing C-u M-v scrolls the calendar backward by a year.

The function keys NEXT and PRIOR are equivalent to C-v and M-v, just as they are in other modes.

The Mark and the Region
-----------------------

The concept of the mark applies to the calendar just as to any other buffer, but it marks a date, not a position in the buffer. The region consists of the days between the mark and point (including the starting and stopping dates).

C-SPC
     Set the mark to today's date (calendar-set-mark).

C-@
     The same.

C-x C-x
     Interchange mark and point (calendar-exchange-point-and-mark).

M-=
     Display the number of days in the current region (calendar-count-days-region).

You set the mark in the calendar, as in any other buffer, by using C-@ or C-SPC (calendar-set-mark).  You return to the marked date with the command C-x C-x (calendar-exchange-point-and-mark) which puts the mark where point was and point where mark was.  The calendar is scrolled as necessary, if the marked date was not visible on the screen.  This does not change the extent of the region.

To determine the number of days in the region, type M-= (calendar-count-days-region).  The numbers of days printed is inclusive; that is, it includes the days specified by mark and point.

The main use of the mark in the calendar is to remember dates that you may want to go back to.  To make this feature more useful, the mark ring (see Mark Ring) operates exactly as in other buffers:  Emacs remembers 16 previous locations of the mark.  To return to a marked date, type C-u C-SPC (or C-u C-@); this is the command calendar-set-mark given a numeric argument.  It moves point to where the mark was, restores the mark from the ring of former marks, and stores the previous point at the end of the mark ring.  So, repeated use of this command moves point through all the old marks on the ring, one by one.

Miscellaneous Calendar Commands
-------------------------------

p d
     Display day-in-year (calendar-print-day-of-year).

?
     Briefly describe calendar commands (describe-calendar-mode).

C-c C-l
     Regenerate the calendar window (redraw-calendar).

SPC
     Scroll the next window (scroll-other-window).

q
     Exit from calendar (exit-calendar).

If you want to know how many days have elapsed since the start of the year, or the number of days remaining in the year, type the p d command (calendar-print-day-of-year).  This displays both of those numbers in the echo area.

To display a brief description of the calendar commands, type ? (describe-calendar-mode).  For a fuller description, type C-h m.

You can use SPC (scroll-other-window) to scroll the other window.  This is handy when you display a list of holidays or diary entries in another window.

If the calendar window text gets corrupted, type C-c C-l (redraw-calendar) to redraw it.  (This can only happen if you use non-Calendar-mode editing commands.)

In Calendar mode, you can use SPC (scroll-other-window) to scroll the other window.  This is handy when you display a list of holidays or diary entries in another window.

To exit from the calendar, type q (exit-calendar).  This buries all buffers related to the calendar, selecting other buffers. (If a frame contains a dedicated calendar window, exiting from the calendar iconifies that frame.)

LaTeX Calendar
==============

The Calendar LaTeX commands produce a buffer of LaTeX code that prints as a calendar.  Depending on the command you use, the printed calendar covers the day, week, month or year that point is in.

t m
     Generate a one-month calendar (cal-tex-cursor-month).

t M
     Generate a sideways-printing one-month calendar (cal-tex-cursor-month-landscape).

t d
     Generate a one-day calendar (cal-tex-cursor-day).

t w 1
     Generate a one-page calendar for one week (cal-tex-cursor-week).

t w 2
     Generate a two-page calendar for one week (cal-tex-cursor-week2).

t w 3
     Generate an ISO-style calendar for one week (cal-tex-cursor-week-iso).

t w 4
     Generate a calendar for one Monday-starting week (cal-tex-cursor-week-monday).

t f w
     Generate a Filofax-style two-weeks-at-a-glance calendar (cal-tex-cursor-filofax-2week).

t f W
     Generate a Filofax-style one-week-at-a-glance calendar (cal-tex-cursor-filofax-week).

t y
     Generate a calendar for one year (cal-tex-cursor-year).

t Y
     Generate a sideways-printing calendar for one year (cal-tex-cursor-year-landscape).

t f y
     Generate a Filofax-style calendar for one year (cal-tex-cursor-filofax-year).

Some of these commands print the calendar sideways (in ``landscape mode''), so it can be wider than it is long.  Some of them use Filofax paper size (3.75in x 6.75in).  All of these commands accept a prefix argument which specifies how many days, weeks, months or years to print (starting always with the selected one).

If the variable cal-tex-holidays is non-nil (the default), then the printed calendars show the holidays in calendar-holidays.  If the variable cal-tex-diary is non-nil (the default is nil), diary entries are included also (in weekly and monthly calendars only).

Holidays
--------

The Emacs calendar knows about all major and many minor holidays, and can display them.

h
     Display holidays for the selected date (calendar-cursor-holidays).

Button2 Holidays
     Display any holidays for the date you click on.

x
     Mark holidays in the calendar window (mark-calendar-holidays).

u
     Unmark calendar window (calendar-unmark).

a
     List all holidays for the displayed three months in another window (list-calendar-holidays).

M-x holidays
     List all holidays for three months around today's date in another window.

M-x list-holidays
     List holidays in another window for a specified range of years.

To see if any holidays fall on a given date, position point on that date in the calendar window and use the h command.  Alternatively, click on that date with Button2 and then choose Holidays from the menu that appears.  Either way, this displays the holidays for that date, in the echo area if they fit there, otherwise in a separate window.

To view the distribution of holidays for all the dates shown in the calendar, use the x command.  This displays the dates that are holidays in a different face (or places a * after these dates, if display with multiple faces is not available). The command applies both to the currently visible months and to other months that subsequently become visible by scrolling.  To turn marking off and erase the current marks, type u, which also erases any diary marks (see Diary).

To get even more detailed information, use the a command, which displays a separate buffer containing a list of all holidays in the current three-month range.  You can use SPC in the calendar window to scroll that list.

The command M-x holidays displays the list of holidays for the current month and the preceding and succeeding months; this works even if you don't have a calendar window.  If you want the list of holidays centered around a different month, use C-u M-x holidays, which prompts for the month and year.

The holidays known to Emacs include United States holidays and the major Christian, Jewish, and Islamic holidays; also the solstices and equinoxes.

The command M-x list-holidays displays the list of holidays for a range of years.  This function asks you for the starting and stopping years, and allows you to choose all the holidays or one of several categories of holidays.  You can use this command even if you don't have a calendar window.

The dates used by Emacs for holidays are based on current practice, not historical fact.  Historically, for instance, the start of daylight savings time and even its existence have varied from year to year, but present United States law mandates that daylight savings time begins on the first Sunday in April.  When the daylight savings rules are set up for the United States, Emacs always uses the present definition, even though it is wrong for some prior years.

Times of Sunrise and Sunset
---------------------------

Special calendar commands can tell you, to within a minute or two, the times of sunrise and sunset for any date.

S
     Display times of sunrise and sunset for the selected date (calendar-sunrise-sunset).

Button2 Sunrise/Sunset
     Display times of sunrise and sunset for the date you click on.

M-x sunrise-sunset
     Display times of sunrise and sunset for today's date.

C-u M-x sunrise-sunset
     Display times of sunrise and sunset for a specified date.

Within the calendar, to display the local times of sunrise and sunset in the echo area, move point to the date you want, and type S.  Alternatively, click Button2 on the date, then choose Sunrise/Sunset from the menu that appears.  The command M-x sunrise-sunset is available outside the calendar to display this information for today's date or a specified date.  To specify a date other than today, use C-u M-x sunrise-sunset, which prompts for the year, month, and day.

You can display the times of sunrise and sunset for any location and any date with C-u C-u M-x sunrise-sunset.  This asks you for a longitude, latitude, number of minutes difference from Coordinated Universal Time, and date, and then tells you the times of sunrise and sunset for that location on that date.

Because the times of sunrise and sunset depend on the location on earth, you need to tell Emacs your latitude, longitude, and location name before using these commands.  Here is an example of what to set:

     (setq calendar-latitude 40.1)
     (setq calendar-longitude -88.2)
     (setq calendar-location-name "Urbana, IL")

Use one decimal place in the values of calendar-latitude and calendar-longitude.

Your time zone also affects the local time of sunrise and sunset. Emacs usually gets time zone information from the operating system, but if these values are not what you want (or if the operating system does not supply them), you must set them yourself.  Here is an example:

     (setq calendar-time-zone -360)
     (setq calendar-standard-time-zone-name "CST")
     (setq calendar-daylight-time-zone-name "CDT")

The value of calendar-time-zone is the number of minutes difference between your local standard time and Coordinated Universal Time (Greenwich time).  The values of calendar-standard-time-zone-name and calendar-daylight-time-zone-name are the abbreviations used in your time zone.  Emacs displays the times of sunrise and sunset corrected for daylight savings time.  See Daylight Savings, for how daylight savings time is determined.

As a user, you might find it convenient to set the calendar location variables for your usual physical location in your init file.  And when you install Emacs on a machine, you can create a default.el file which sets them properly for the typical location of most users of that machine.  See Init File.

Phases of the Moon
------------------

These calendar commands display the dates and times of the phases of the moon (new moon, first quarter, full moon, last quarter).  This feature is useful for debugging problems that ``depend on the phase of the moon.''

M
     Display the dates and times for all the quarters of the moon for the three-month period shown (calendar-phases-of-moon).

M-x phases-of-moon
     Display dates and times of the quarters of the moon for three months around today's date.

Within the calendar, use the M command to display a separate buffer of the phases of the moon for the current three-month range.  The dates and times listed are accurate to within a few minutes.

Outside the calendar, use the command M-x phases-of-moon to display the list of the phases of the moon for the current month and the preceding and succeeding months.  For information about a different month, use C-u M-x phases-of-moon, which prompts for the month and year.

The dates and times given for the phases of the moon are given in local time (corrected for daylight savings, when appropriate); but if the variable calendar-time-zone is void, Coordinated Universal Time (the Greenwich time zone) is used.  See Daylight Savings.

Conversion To and From Other Calendars
--------------------------------------

The Emacs calendar displayed is always the Gregorian calendar, sometimes called the ``new style'' calendar, which is used in most of the world today.  However, this calendar did not exist before the sixteenth century and was not widely used before the eighteenth century; it did not fully displace the Julian calendar and gain universal acceptance until the early twentieth century.  The Emacs calendar can display any month since January, year 1 of the current era, but the calendar displayed is the Gregorian, even for a date at which the Gregorian calendar did not exist.

While Emacs cannot display other calendars, it can convert dates to and from several other calendars.

If you are interested in these calendars, you can convert dates one at a time.  Put point on the desired date of the Gregorian calendar and press the appropriate keys.  The p is a mnemonic for ``print'' since Emacs ``prints' the equivalent date in the echo area.

Supported Calendar Systems
==========================

The ISO commercial calendar is used largely in Europe.

The Julian calendar, named after Julius Caesar, was the one used in Europe throughout medieval times, and in many countries up until the nineteenth century.

Astronomers use a simple counting of days elapsed since noon, Monday, January 1, 4713 B.C. on the Julian calendar.  The number of days elapsed is called the Julian day number or the Astronomical day number.

The Hebrew calendar is used by tradition in the Jewish religion.  The Emacs calendar program uses the Hebrew calendar to determine the dates of Jewish holidays.  Hebrew calendar dates begin and end at sunset.

The Islamic calendar is used in many predominantly Islamic countries. Emacs uses it to determine the dates of Islamic holidays.  There is no universal agreement in the Islamic world about the calendar; Emacs uses a widely accepted version, but the precise dates of Islamic holidays often depend on proclamation by religious authorities, not on calculations.  As a consequence, the actual dates of observance can vary slightly from the dates computed by Emacs.  Islamic calendar dates begin and end at sunset.

The French Revolutionary calendar was created by the Jacobins after the 1789 revolution, to represent a more secular and nature-based view of the annual cycle, and to install a 10-day week in a rationalization measure similar to the metric system.  The French government officially abandoned this calendar at the end of 1805.

The Maya of Central America used three separate, overlapping calendar systems, the long count, the tzolkin, and the haab. Emacs knows about all three of these calendars.  Experts dispute the exact correlation between the Mayan calendar and our calendar; Emacs uses the Goodman-Martinez-Thompson correlation in its calculations.

The Copts use a calendar based on the ancient Egyptian solar calendar. Their calendar consists of twelve 30-day months followed by an extra five-day period.  Once every fourth year they add a leap day to this extra period to make it six days.  The Ethiopic calendar is identical in structure, but has different year numbers and month names.

The Persians use a solar calendar based on a design of Omar Khayyam. Their calendar consists of twelve months of which the first six have 31 days, the next five have 30 days, and the last has 29 in ordinary years and 30 in leap years.  Leap years occur in a complicated pattern every four or five years.

The Chinese calendar is a complicated system of lunar months arranged into solar years.  The years go in cycles of sixty, each year containing either twelve months in an ordinary year or thirteen months in a leap year; each month has either 29 or 30 days.  Years, ordinary months, and days are named by combining one of ten ``celestial stems'' with one of twelve ``terrestrial branches'' for a total of sixty names that are repeated in a cycle of sixty.

Converting To Other Calendars
=============================

The following commands describe the selected date (the date at point) in various other calendar systems:

Button2  Other Calendars
     Display the date that you click on, expressed in various other calendars.

p c
     Display ISO commercial calendar equivalent for selected day (calendar-print-iso-date).

p j
     Display Julian date for selected day (calendar-print-julian-date).

p a
     Display astronomical (Julian) day number for selected day (calendar-print-astro-day-number).

p h
     Display Hebrew date for selected day (calendar-print-hebrew-date).

p i
     Display Islamic date for selected day (calendar-print-islamic-date).

p f
     Display French Revolutionary date for selected day (calendar-print-french-date).

p C
     Display Chinese date for selected day (calendar-print-chinese-date).

p k
     Display Coptic date for selected day (calendar-print-coptic-date).

p e
     Display Ethiopic date for selected day (calendar-print-ethiopic-date).

p p
     Display Persian date for selected day (calendar-print-persian-date).

p m
     Display Mayan date for selected day (calendar-print-mayan-date).

If you are using X, the easiest way to translate a date into other calendars is to click on it with Button2, then choose Other Calendars from the menu that appears.  This displays the equivalent forms of the date in all the calendars Emacs understands, in the form of a menu.  (Choosing an alternative from this menu doesn't actually do anything---the menu is used only for display.)

Put point on the desired date of the Gregorian calendar, then type the appropriate keys.  The p is a mnemonic for ``print'' since Emacs ``prints'' the equivalent date in the echo area.

Converting From Other Calendars
===============================

You can use the other supported calendars to specify a date to move to.  This section describes the commands for doing this using calendars other than Mayan; for the Mayan calendar, see the following section.

g c
     Move to a date specified in the ISO commercial calendar (calendar-goto-iso-date).

g j
     Move to a date specified in the Julian calendar (calendar-goto-julian-date).

g a
     Move to a date specified in astronomical (Julian) day number (calendar-goto-astro-day-number).

g h
     Move to a date specified in the Hebrew calendar (calendar-goto-hebrew-date).

g i
     Move to a date specified in the Islamic calendar (calendar-goto-islamic-date).

g f
     Move to a date specified in the French Revolutionary calendar (calendar-goto-french-date).

g C
     Move to a date specified in the Chinese calendar (calendar-goto-chinese-date).

g p
     Move to a date specified in the Persian calendar (calendar-goto-persian-date).

g k
     Move to a date specified in the Coptic calendar (calendar-goto-coptic-date).

g e
     Move to a date specified in the Ethiopic calendar (calendar-goto-ethiopic-date).

These commands ask you for a date on the other calendar, move point to the Gregorian calendar date equivalent to that date, and display the other calendar's date in the echo area.  Emacs uses strict completion (see Completion) whenever it asks you to type a month name, so you don't have to worry about the spelling of Hebrew, Islamic, or French names.

One common question concerning the Hebrew calendar is the computation of the anniversary of a date of death, called a ``yahrzeit.''  The Emacs calendar includes a facility for such calculations.  If you are in the calendar, the command M-x list-yahrzeit-dates asks you for a range of years and then displays a list of the yahrzeit dates for those years for the date given by point.  If you are not in the calendar, this command first asks you for the date of death and the range of years, and then displays the list of yahrzeit dates.

Converting from the Mayan Calendar
----------------------------------

Here are the commands to select dates based on the Mayan calendar:

g m l
     Move to a date specified by the long count calendar (calendar-goto-mayan-long-count-date).

g m n t
     Move to the next occurrence of a place in the tzolkin calendar (calendar-next-tzolkin-date).

g m p t
     Move to the previous occurrence of a place in the tzolkin calendar (calendar-previous-tzolkin-date).

g m n h
     Move to the next occurrence of a place in the haab calendar (calendar-next-haab-date).

g m p h
     Move to the previous occurrence of a place in the haab calendar (calendar-previous-haab-date).

g m n c
     Move to the next occurrence of a place in the calendar round (calendar-next-calendar-round-date).

g m p c
     Move to the previous occurrence of a place in the calendar round (calendar-previous-calendar-round-date).

To understand these commands, you need to understand the Mayan calendars. The long count is a counting of days with these units:

     1 kin = 1 day   1 uinal = 20 kin   1 tun = 18 uinal
     1 katun = 20 tun   1 baktun = 20 katun

Thus, the long count date 12.16.11.16.6 means 12 baktun, 16 katun, 11 tun, 16 uinal, and 6 kin.  The Emacs calendar can handle Mayan long count dates as early as 7.17.18.13.1, but no earlier.  When you use the g m l command, type the Mayan long count date with the baktun, katun, tun, uinal, and kin separated by periods.

The Mayan tzolkin calendar is a cycle of 260 days formed by a pair of independent cycles of 13 and 20 days.  Since this cycle repeats endlessly, Emacs provides commands to move backward and forward to the previous or next point in the cycle.  Type g m p t to go to the previous tzolkin date; Emacs asks you for a tzolkin date and moves point to the previous occurrence of that date.  Similarly, type g m n t to go to the next occurrence of a tzolkin date.

The Mayan haab calendar is a cycle of 365 days arranged as 18 months of 20 days each, followed a 5-day monthless period.  Like the tzolkin cycle, this cycle repeats endlessly, and there are commands to move backward and forward to the previous or next point in the cycle.  Type g m p h to go to the previous haab date; Emacs asks you for a haab date and moves point to the previous occurrence of that date. Similarly, type g m n h to go to the next occurrence of a haab date.

The Maya also used the combination of the tzolkin date and the haab date.  This combination is a cycle of about 52 years called a calendar round.  If you type g m p c, Emacs asks you for both a haab and a tzolkin date and then moves point to the previous occurrence of that combination.  Use g m n c to move point to the next occurrence of a combination.  These commands signal an error if the haab/tzolkin date combination you have typed is impossible.

Emacs uses strict completion (see Completion) whenever it asks you to type a Mayan name, so you don't have to worry about spelling.

The Diary
---------

The Emacs diary keeps track of appointments or other events on a daily basis, in conjunction with the calendar.  To use the diary feature, you must first create a diary file containing a list of events and their dates.  Then Emacs can automatically pick out and display the events for today, for the immediate future, or for any specified date.

By default, Emacs uses ~/diary as the diary file.  This is the same file that the calendar utility uses.  A sample ~/diary file is:

     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.

This example uses extra spaces to align the event descriptions of most of the entries.  Such formatting is purely a matter of taste.

Although you probably will start by creating a diary manually, Emacs provides a number of commands to let you view, add, and change diary entries.  You can also share diary entries with other users (see Included Diary Files).

Commands Displaying Diary Entries
---------------------------------

Once you have created a ~/diary file, you can use the calendar to view it.  You can also view today's events outside of Calendar mode.

d
     Display all diary entries for the selected date (view-diary-entries).

Button2 Diary
     Display all diary entries for the date you click on.

s
     Display the entire diary file (show-all-diary-entries).

m
     Mark all visible dates that have diary entries (mark-diary-entries).

u
     Unmark the calendar window (calendar-unmark).

M-x print-diary-entries
     Print hard copy of the diary display as it appears.

M-x diary
     Display all diary entries for today's date.

M-x diary-mail-entries
     Mail yourself email reminders about upcoming diary entries.

Displaying the diary entries with d shows in a separate window the diary entries for the selected date in the calendar.  The mode line of the new window shows the date of the diary entries and any holidays that fall on that date.  If you specify a numeric argument with d, it shows all the diary entries for that many successive days.  Thus, 2 d displays all the entries for the selected date and for the following day.

Another way to display the diary entries for a date is to click Button2 on the date, and then choose Diary from the menu that appears.

To get a broader view of which days are mentioned in the diary, use the m command.  This displays the dates that have diary entries in a different face (or places a + after these dates, if display with multiple faces is not available).  The command applies both to the currently visible months and to other months that subsequently become visible by scrolling.  To turn marking off and erase the current marks, type u, which also turns off holiday marks (see Holidays).

To see the full diary file, rather than just some of the entries, use the s command.

Display of selected diary entries uses the selective display feature to hide entries that don't apply.

The diary buffer as you see it is an illusion, so simply printing the buffer does not print what you see on your screen.  There is a special command to print hard copy of the diary buffer as it appears; this command is M-x print-diary-entries.  It sends the data directly to the printer.  You can customize it like lpr-region (see Hardcopy).

The command M-x diary displays the diary entries for the current date, independently of the calendar display, and optionally for the next few days as well; the variable number-of-diary-entries specifies how many days to include (see Customization).

If you put (diary) in your init file, this automatically displays a window with the day's diary entries, when you enter Emacs.  See Init File.  The mode line of the displayed window shows the date and any holidays that fall on that date.

Many users like to receive notice of events in their diary as email. To send such mail to yourself, use the command M-x diary-mail-entries.  A prefix argument specifies how many days (starting with today) to check; otherwise, the variable diary-mail-days says how many days.

The Diary File
--------------

Your diary file is a file that records events associated with particular dates.  The name of the diary file is specified by the variable diary-file; ~/diary is the default.  The calendar utility program supports a subset of the format allowed by the Emacs diary facilities, so you can use that utility to view the diary file, with reasonable results aside from the entries it cannot understand.

Each entry in the diary file describes one event and consists of one or more lines.  An entry always begins with a date specification at the left margin.  The rest of the entry is simply text to describe the event.  If the entry has more than one line, then the lines after the first must begin with whitespace to indicate they continue a previous entry.  Lines that do not begin with valid dates and do not continue a preceding entry are ignored.

You can inhibit the marking of certain diary entries in the calendar window; to do this, insert an ampersand (&) at the beginning of the entry, before the date.  This has no effect on display of the entry in the diary window; it affects only marks on dates in the calendar window.  Nonmarking entries are especially useful for generic entries that would otherwise mark many different dates.

If the first line of a diary entry consists only of the date or day name with no following blanks or punctuation, then the diary window display doesn't include that line; only the continuation lines appear. For example, this entry:

     02/11/1989
           Bill B. visits Princeton today
           2pm Cognitive Studies Committee meeting
           2:30-5:30 Liz at Lawrenceville
           4:00pm Dentist appt
           7:30pm Dinner at George's
           8:00-10:00pm concert

appears in the diary window without the date line at the beginning. This style of entry looks neater when you display just a single day's entries, but can cause confusion if you ask for more than one day's entries.

You can edit the diary entries as they appear in the window, but it is important to remember that the buffer displayed contains the entire diary file, with portions of it concealed from view.  This means, for instance, that the C-f (forward-char) command can put point 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 cannot cause problems, but editing at the end of a line may not do what you expect.  Deleting a line may delete other invisible entries that follow it.  Before editing the diary, it is best to display the entire file with s (show-all-diary-entries).

Date Formats
------------

Here are some sample diary entries, illustrating different ways of formatting a date.  The examples all show dates in American order (month, day, year), but Calendar mode supports European order (day, month, year) as an option.

     4/20/93  Switch-over to new tabulation system
     apr. 25  Start tabulating annual results
     4/30  Results for April are due
     */25  Monthly cycle finishes
     Friday  Don't leave without backing up files

The first entry appears only once, on April 20, 1993.  The second and third appear every year on the specified dates, and the fourth uses a wildcard (asterisk) for the month, so it appears on the 25th of every month.  The final entry appears every week on Friday.

You can use just numbers to express a date, as in MONTH/DAY or MONTH/DAY/YEAR. This must be followed by a nondigit.  In the date itself, MONTH and DAY are numbers of one or two digits.  The optional YEAR is also a number, and may be abbreviated to the last two digits; that is, you can use 11/12/1989 or 11/12/89.

Dates can also have the form MONTHNAME DAY or MONTHNAME DAY, YEAR, where the month's name can be spelled in full or abbreviated to three characters (with or without a period).  Case is not significant.

A date may be generic; that is, partially unspecified.  Then the entry applies to all dates that match the specification.  If the date does not contain a year, it is generic and applies to any year. Alternatively, MONTH, DAY, or YEAR can be a *; this matches any month, day, or year, respectively.  Thus, a diary entry 3/*/* matches any day in March of any year; so does march *.

If you prefer the European style of writing dates---in which the day comes before the month---type M-x european-calendar while in the calendar, or set the variable european-calendar-style to t before using any calendar or diary command.  This mode interprets all dates in the diary in the European manner, and also uses European style for displaying diary dates.  (Note that there is no comma after the MONTHNAME in the European style.)  To go back to the (default) American style of writing dates, type M-x american-calendar.

You can use the name of a day of the week as a generic date which applies to any date falling on that day of the week.  You can abbreviate the day of the week to three letters (with or without a period) or spell it in full; case is not significant.

Commands to Add to the Diary
----------------------------

While in the calendar, there are several commands to create diary entries:

i d
     Add a diary entry for the selected date (insert-diary-entry).

i w
     Add a diary entry for the selected day of the week (insert-weekly-diary-entry).

i m
     Add a diary entry for the selected day of the month (insert-monthly-diary-entry).

i y
     Add a diary entry for the selected day of the year (insert-yearly-diary-entry).

You can make a diary entry for a specific date by selecting that date in the calendar window and typing the i d command.  This command displays the end of your diary file in another window and inserts the date; you can then type the rest of the diary entry.

If you want to make a diary entry that applies to a specific day of the week, select that day of the week (any occurrence will do) and type i w.  This inserts the day-of-week as a generic date; you can then type the rest of the diary entry.  You can make a monthly diary entry in the same fashion.  Select the day of the month, use the i m command, and type rest of the entry.  Similarly, you can insert a yearly diary entry with the i y command.

All of the above commands make marking diary entries by default.  To make a nonmarking diary entry, give a numeric argument to the command. For example, C-u i w makes a nonmarking weekly diary entry.

When you modify the diary file, be sure to save the file before exiting Emacs.

Special Diary Entries
---------------------

In addition to entries based on calendar dates, the diary file can contain sexp entries for regular events such as anniversaries. These entries are based on Lisp expressions (sexps) that Emacs evaluates as it scans the diary file.  Instead of a date, a sexp entry contains %% followed by a Lisp expression which must begin and end with parentheses.  The Lisp expression determines which dates the entry applies to.

Calendar mode provides commands to insert certain commonly used sexp entries:

i a
     Add an anniversary diary entry for the selected date (insert-anniversary-diary-entry).

i b
     Add a block diary entry for the current region (insert-block-diary-entry).

i c
     Add a cyclic diary entry starting at the date (insert-cyclic-diary-entry).

If you want to make a diary entry that applies to the anniversary of a specific date, move point to that date and use the i a command. This displays the end of your diary file in another window and inserts the anniversary description; you can then type the rest of the diary entry. The entry looks like this:

The effect of i a is to add a diary-anniversary sexp to your diary file.  You can also add one manually, for instance:

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

This entry applies to October 31 in any year after 1948; 10 31 1948 specifies the date.  (If you are using the European calendar style, the month and day are interchanged.)  The reason this expression requires a beginning year is that advanced diary functions can use it to calculate the number of elapsed years.

A block diary entry applies to a specified range of consecutive dates.  Here is a block diary entry that applies to all dates from June 24, 1990 through July 10, 1990:

     %%(diary-block 6 24 1990 7 10 1990) Vacation

The 6 24 1990 indicates the starting date and the 7 10 1990 indicates the stopping date.  (Again, if you are using the European calendar style, the month and day are interchanged.)

To insert a block entry, place point and the mark on the two dates that begin and end the range, and type i b.  This command displays the end of your diary file in another window and inserts the block description; you can then type the diary entry.

Cyclic diary entries repeat after a fixed interval of days.  To create one, select the starting date and use the i c command.  The command prompts for the length of interval, then inserts the entry, which looks like this:

     %%(diary-cyclic 50 3 1 1990) Renew medication

This entry applies to March 1, 1990 and every 50th day following; 3 1 1990 specifies the starting date.  (If you are using the European calendar style, the month and day are interchanged.)

All three of these commands make marking diary entries.  To insert a nonmarking entry, give a numeric argument to the command.  For example, C-u i a makes a nonmarking anniversary diary entry.

Marking sexp diary entries in the calendar is extremely time-consuming, since every date visible in the calendar window must be individually checked.  So it's a good idea to make sexp diary entries nonmarking (with &) when possible.

Another sophisticated kind of sexp entry, a floating diary entry, specifies a regularly occurring event by offsets specified in days, weeks, and months.  It is comparable to a crontab entry interpreted by the cron utility.  Here is a nonmarking, floating diary entry that applies to the last Thursday in November:

     &%%(diary-float 11 4 -1) American Thanksgiving

The 11 specifies November (the eleventh month), the 4 specifies Thursday (the fourth day of the week, where Sunday is numbered zero), and the -1 specifies ``last'' (1 would mean ``first'', 2 would mean ``second'', -2 would mean ``second-to-last'', and so on).  The month can be a single month or a list of months.  Thus you could change the 11 above to '(1 2 3) and have the entry apply to the last Thursday of January, February, and March.  If the month is t, the entry applies to all months of the year.

The sexp feature of the diary allows you to specify diary entries based on any Emacs Lisp expression.  You can use the library of built-in functions or you can write your own functions.  The built-in functions include the ones shown in this section, plus a few others (see Sexp Diary Entries).

The generality of sexps lets you specify any diary entry that you can describe algorithmically.  Suppose you get paid on the 21st of the month if it is a weekday, and to the Friday before if the 21st is on a weekend.  The diary entry

     &%%(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

to just those dates.  This example illustrates how the sexp can depend on the variable date; this variable is a list (MONTH DAY YEAR) that gives the Gregorian date for which the diary entries are being found.  If the value of the sexp is t, the entry applies to that date.  If the sexp evaluates to nil, the entry does not apply to that date.

Customizing the Calendar and Diary
----------------------------------

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

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.  See Init File.

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 Faces), if the display supports that, or by placing a plus sign (+) beside the date otherwise.

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, when Emacs supports multiple faces on your terminal.

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 when Emacs supports multiple faces on your terminal.

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

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")))

See 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") ... )

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))

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.

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.

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 Regexps) 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"))

Emacs matches of the diary entries with the date forms is done with the standard syntax table from Fundamental mode (see Syntax Tables (XEmacs Lisp Reference Manual)), but with the * changed so that it is a word constituent.

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.

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  Islamic-date diary entry  that matches Dhu al-Qada 25:

     IDhu al-Qada 25 Happy Islamic birthday!

and would appear in the diary for any date that corresponds to Dhu al-Qada 25 on the Islamic calendar.

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.

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 by positioning 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.  Add this line to your init file:

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

See Init File.

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.

Included Diary Files
....................

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.

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.

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

applies to just those dates.  This example illustrates how the sexp can depend on the variable date; this variable is a list (MONTH DAY YEAR) that gives the Gregorian date for which the diary entries are being found.  If the value of the expression is t, the entry applies to that date.  If the expression evaluates to nil, the entry does not apply to that date.

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.)

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 t (the default), Emacs rings the terminal bell for appointment reminders.

appt-visible
     If this is t (the default), Emacs displays the appointment message in echo area.

appt-display-mode-line
     If this is t (the default), Emacs displays the number of minutes to the appointment on the mode line.

appt-msg-window
     If this is t (the default), Emacs displays the appointment message in another window.

appt-display-duration
     The number of seconds an appointment message is displayed.  The default is 5 seconds.