(command-line): If no error data, print "", not nil.

[gnu-emacs] / lispref / calendar.texi

@c -*-texinfo-*-
@c This is part of the GNU Emacs Lisp Reference Manual.
@c Copyright (C) 1990, 1991, 1992, 1993 Free Software Foundation, Inc. 
@c See the file elisp.texi for copying conditions.
@node Calendar, Tips, Display, Top
@chapter Customizing the Calendar and Diary

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

@menu
* Calendar Customizing::   Defaults you can set.
* Holiday Customizing::    Defining your own holidays.
* Date Display Format::    Changing the format.
* Time Display Format::    Changing the format.
* Daylight Savings::       Changing the default.
* Diary Customizing::      Defaults you can set.
* Hebrew/Islamic Entries:: How to obtain them.
* Fancy Diary Display::    Enhancing the diary display, sorting entries.
* Included Diary Files::   Sharing a common diary file.
* Sexp Diary Entries::     Fancy things you can do.
* Appt Customizing::       Customizing appointment reminders.
@end menu

@node Calendar Customizing
@section Customizing the Calendar
@vindex view-diary-entries-initially

  If you set the variable @code{view-diary-entries-initially} to
@code{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 @file{.emacs} file:@refill

@example
(setq view-diary-entries-initially t)
(calendar)
@end example

@noindent
they display both the calendar and diary windows whenever you start Emacs.

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

@vindex mark-diary-entries-in-calendar
  You can set the variable @code{mark-diary-entries-in-calendar} to @code{t}
in order to place a plus sign (@samp{+}) beside any dates with diary entries.
Whenever the calendar window is displayed or redisplayed, the diary entries
are automatically marked for holidays.

@vindex mark-holidays-in-calendar
  Similarly, setting the variable @code{mark-holidays-in-calendar} to
@code{t} places an asterisk (@samp{*}) after all holiday dates visible
in the calendar window.

@vindex calendar-load-hook
  There are many customizations that you can make with the hooks
provided.  For example, the variable @code{calendar-load-hook}, whose
default value is @code{nil}, is a normal hook run when the calendar
package is first loaded (before actually starting to display the
calendar).

@vindex initial-calendar-window-hook
  The variable @code{initial-calendar-window-hook}, whose default value
is @code{nil}, is a normal hook run the first time the calendar window
is displayed.  The function is invoked only when you first enter
Calendar mode, not when you redisplay an existing Calendar window.  But
if you leave the calendar with the @kbd{q} command and reenter it, the
hook runs again.@refill

@vindex today-visible-calendar-hook
  The variable @code{today-visible-calendar-hook}, whose default value
is @code{nil}, 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;
a function @code{calendar-star-date} is included for this purpose.  In
your @file{.emacs} file, put:@refill

@findex calendar-star-date
@example
(setq today-visible-calendar-hook 'calendar-star-date)
@end example

@noindent
Another standard hook function adds asterisks around the current date.
Here's how to use it:

@findex calendar-mark-today
@example
(setq today-visible-calendar-hook 'calendar-mark-today)
@end example

@vindex today-invisible-calendar-hook
@noindent
  A corresponding variable, @code{today-invisible-calendar-hook}, whose
default value is @code{nil}, is a normal hook run after the calendar
buffer text has been prepared, if the current date is @emph{not} visible
in the window.@refill

@node Holiday Customizing
@section Customizing the Holidays

@vindex calendar-holidays
@vindex christian-holidays
@vindex hebrew-holidays
@vindex islamic-holidays
  Emacs knows about holidays defined by entries on one of several lists.
You can customize theses lists of holidays to your own needs, adding
holidays or deleting lists of holidays.  The lists of holidays that
Emacs uses are for general holidays (@code{general-holidays}), local
holidays (@code{local-holidays}), Christian holidays
(@code{christian-holidays}), Hebrew (Jewish) holidays
(@code{hebrew-holidays}), Islamic (Moslem) holidays
(@code{islamic-holidays}), and other holidays (@code{other-holidays}).

@vindex general-holidays
  The general holidays are, by default, holidays common throughout the
United States.  To eliminate these holidays, set @code{general-holidays}
to @code{nil}.

@vindex local-holidays
  There are no default local holidays (but sites may supply some).  You
can set the variable @code{local-holidays} to any list of holidays, as
described below.

@vindex all-christian-calendar-holidays
@vindex all-hebrew-calendar-holidays
@vindex all-islamic-calendar-holidays
  By default, Emacs does not consider all the holidays of these
religions, only those commonly found in secular calendars.  For a more
extensive collection of religious holidays, you can set any (or all) of
the variables @code{all-christian-calendar-holidays},
@code{all-hebrew-calendar-holidays}, or
@code{all-islamic-calendar-holidays} to @code{t}.  If you want to
eliminate the religious holidays, set any or all of the corresponding
variables @code{christian-holidays}, @code{hebrew-holidays}, and
@code{islamic-holidays} to @code{nil}.@refill

@vindex other-holidays
  You can set the variable @code{other-holidays} to any list of
holidays.  This list, normally empty, is intended for your use.

@cindex holiday forms
  Each of the lists (@code{general-holidays}, @code{local-holidays},
@code{christian-holidays}, @code{hebrew-holidays},
@code{islamic-holidays}, and @code{other-holidays}) is a list of
@dfn{holiday forms}, each holiday form describing a holiday (or
sometimes a list of holidays).  Holiday forms may have the following
formats:

@table @code
@item (holiday-fixed @var{month} @var{day} @var{string})
A fixed date on the Gregorian calendar.  @var{month} and @var{day} are
numbers, @var{string} is the name of the holiday.

@item (holiday-float @var{month} @var{dayname} @var{k} @var{string})
The @var{k}th @var{dayname} in @var{month} on the Gregorian calendar
(@var{dayname}=0 for Sunday, and so on); negative @var{k} means count back
from the end of the month.  @var{string} is the name of the holiday.

@item (holiday-hebrew @var{month} @var{day} @var{string})
A fixed date on the Hebrew calendar.  @var{month} and @var{day} are
numbers, @var{string} is the name of the holiday.

@item (holiday-islamic @var{month} @var{day} @var{string})
A fixed date on the Islamic calendar.  @var{month} and @var{day} are
numbers, @var{string} is the name of the holiday.

@item (holiday-julian @var{month} @var{day} @var{string})
A fixed date on the Julian calendar.  @var{month} and @var{day} are
numbers, @var{string} is the name of the holiday.

@item (holiday-sexp @var{sexp} @var{string})
@var{sexp} is a Lisp expression that should use the variable @code{year}
to compute the date of a holiday, or @code{nil} if the holiday doesn't
happen this year.  The value represents the date as a list of the form
@code{(@var{month} @var{day} @var{year})}.  @var{string} is the name of
the holiday.

@item (if @var{boolean} @var{holiday-form} &optional @var{holiday-form})
A choice between two holidays based on the value of @var{boolean}.

@item (@var{function} &optional @var{args})
Dates requiring special computation; @var{args}, if any, are passed in
a list to the function @code{calendar-holiday-function-@var{function}}.
@end table

  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 @file{.emacs} file:

@smallexample
(setq other-holidays '((holiday-fixed 7 14 "Bastille Day")))
@end smallexample

@noindent
The holiday form @code{(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:

@smallexample
(holiday-float 8 1 4 "Hurricane Supplication Day")
@end smallexample

@noindent
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,
@minus{}1 the last occurrence, @minus{}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,

@smallexample
(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")))
@end smallexample

@noindent
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 the @samp{if} or the
@samp{sexp} form.  For example, American presidential elections occur on
the first Tuesday after the first Monday in November of years divisible
by 4:

@smallexample
(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"))
@end smallexample

@noindent
or

@smallexample
(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"))
@end smallexample

  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 of the sun, for example, add @code{(eclipses)} to
@code{other-holidays} and write an Emacs Lisp function
@code{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:

@smallexample
(((6 27 1991) "Lunar Eclipse") ((7 11 1991) "Solar Eclipse") ... )
@end smallexample

@node Date Display Format
@section Date Display Format
@vindex calendar-date-display-form

  You can customize the manner of displaying dates in the diary,
in mode lines, and in messages by setting
@code{calendar-date-display-form}.  This variable is a list of
expressions that can involve the variables @code{month}, @code{day}, and
@code{year}, all numbers in string form, and @code{monthname} and
@code{dayname}, both alphabetic strings.  In the American style, the
default value of this list is as follows:

@smallexample
((if dayname (concat dayname ", ")) monthname " " day ", " year)
@end smallexample

@noindent
while in the European style this value is the default:

@smallexample
((if dayname (concat dayname ", ")) day " " monthname " " year)
@end smallexample

The ISO standard date representation is this:

@smallexample
(year "-" month "-" day)
@end smallexample

@noindent
This specifies a typical American format:

@smallexample
(month "/" day "/" (substring year -2))
@end smallexample

@node Time Display Format
@section Time Display Format
@vindex calendar-time-display-form

  In the calendar, diary, and related buffers, Emacs displays times of
day in the conventional American style with the hours from 1 through 12,
minutes, and either @samp{am} or @samp{pm}.  If you prefer the
``military'' (European) style of writing times---in which the hours go
from 00 to 23---you can alter the variable
@code{calendar-time-display-form}.  This variable is a list of
expressions that can involve the variables @code{12-hours},
@code{24-hours}, and @code{minutes}, all numbers in string form, and
@code{am-pm} and @code{time-zone}, both alphabetic strings.  The default
definition of @code{calendar-time-display-form} is as follows:

@smallexample
(12-hours ":" minutes am-pm
          (if time-zone " (") time-zone (if time-zone ")"))
@end smallexample

  Setting @code{calendar-time-display-form} to

@smallexample
(24-hours ":" minutes
          (if time-zone " (") time-zone (if time-zone ")"))
@end smallexample

@noindent
gives military-style times like @samp{21:07 (UT)} if time zone names are
defined, and times like @samp{21:07} if they are not.

@node Daylight Savings
@section Daylight Savings Time
@cindex 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 default choice of rules is not
appropriate for your location, you can tell Emacs the rules to use by
setting certain variables.

@vindex calendar-daylight-savings-starts
@vindex calendar-daylight-savings-ends
  These variables are @code{calendar-daylight-savings-starts} together
with @code{calendar-daylight-savings-ends}.  Their values should be Lisp
expressions that refer to the variable @code{year}, and evaluate to the
Gregorian date on which daylight savings time starts or (respectively)
ends, in the form of a list @code{(@var{month} @var{day} @var{year})}.
The values should be @code{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:

@example
@group
(calendar-nth-named-day 1 0 4 year)
(calendar-nth-named-day -1 0 10 year)
@end group
@end example

@noindent
i.e., the first 0th day (Sunday) of the fourth month (April) in
the year specified by @code{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
@code{calendar-daylight-savings-starts} to this:

@example
(list 10 1 year)
@end example

  For a more complex example, suppose daylight savings time begins on
the first of Nisan on the Hebrew calendar.  You would set
@code{calendar-daylight-savings-starts} as follows:

@example
(calendar-gregorian-from-absolute
  (calendar-absolute-from-hebrew
    (list 1 1 (+ year 3760))))
@end example

@noindent
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 @code{calendar-daylight-savings-starts}
and @code{calendar-daylight-savings-ends} to @code{nil}.

@vindex calendar-daylight-time-offset
  This variable specifies the difference between daylight savings time and
standard time, measured in minutes.  The value for Cambridge is 60.

@vindex calendar-daylight-savings-starts-time
@vindex calendar-daylight-savings-ends-time
  These variables specify is 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.

@node Diary Customizing
@section Customizing the Diary

@vindex holidays-in-diary-buffer
  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 @code{holidays-in-diary-buffer} to
@code{nil}.@refill

@vindex number-of-diary-entries
  The variable @code{number-of-diary-entries} controls the number of
days of diary entries to be displayed at one time.  It affects the
initial display when @code{view-diary-entries-initially} is @code{t}, as
well as the command @kbd{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: if the
value is @code{[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.

@vindex print-diary-entries-hook
@findex print-diary-entries
  The variable @code{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 @code{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.

@vindex diary-date-forms
  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 @code{diary-date-forms}.  This variable is a list of forms of
dates recognized in the diary file.  Each form is a list of regular
expressions (@pxref{Regular Expressions}) and the variables
@code{month}, @code{day}, @code{year}, @code{monthname}, and
@code{dayname}.  The variable @code{monthname} matches the name of the
month, capitalized or not, or its three-letter abbreviation, followed by
a period or not; it matches @samp{*}.  Similarly, @code{dayname} matches
the name of the day, capitalized or not, or its three-letter
abbreviation, followed by a period or not.  The variables @code{month},
@code{day}, and @code{year} match those numerical values, preceded by
arbitrarily many zeros; they also match @samp{*}.  The default value of
@code{diary-date-forms} in the American style is

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

@noindent
Emacs matches of the diary entries with the date forms is done with the
standard syntax table from Fundamental mode (@pxref{Syntax Tables}), but
with the @samp{*} changed so that it is a word constituent.

  The forms on the list must be @emph{mutually exclusive} and must not
match any portion of the diary entry itself, just the date.  If, to be
mutually exclusive, the pattern must match a portion of the diary entry
itself, the first element of the form @emph{must} be @code{backup}.
This causes the date recognizer to back up to the beginning of the
current word of the diary entry.  Even if you use @code{backup}, the
form must absolutely not match more than a portion of the first word of
the diary entry.  The default value of @code{diary-date-forms} in the
European style is this list:

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

@noindent
Notice the use of @code{backup} in the middle form because part of the
diary entry must be matched to distinguish this form from the following one.

@node Hebrew/Islamic Entries
@section Hebrew- and Islamic-Date Diary Entries

  Your diary file can have entries based on Hebrew or Islamic dates, as
well as entries based on our usual Gregorian calendar.  However, because
the processing of such entries is time-consuming and most people don't
need them, you must customize the processing of your diary file to
specify that you want such entries recognized.  If you want Hebrew-date
diary entries, for example, you must include these lines in your
@file{.emacs} file:

@vindex nongregorian-diary-listing-hook
@vindex nongregorian-diary-marking-hook
@findex list-hebrew-diary-entries
@findex mark-hebrew-diary-entries
@smallexample
(setq nongregorian-diary-listing-hook 'list-hebrew-diary-entries)
(setq nongregorian-diary-marking-hook 'mark-hebrew-diary-entries)
@end smallexample

@noindent
If you want Islamic-date entries, include these lines in your
@file{.emacs} file:

@findex list-islamic-diary-entries
@findex mark-islamic-diary-entries
@smallexample
(setq nongregorian-diary-listing-hook 'list-islamic-diary-entries)
(setq nongregorian-diary-marking-hook 'mark-islamic-diary-entries)
@end smallexample

@noindent
If you want both Hebrew- and Islamic-date entries, include these lines:

@smallexample
(setq nongregorian-diary-listing-hook
      '(list-hebrew-diary-entries list-islamic-diary-entries))
(setq nongregorian-diary-marking-hook
      '(mark-hebrew-diary-entries mark-islamic-diary-entries))
@end smallexample

  Hebrew- and Islamic-date diary entries have the same formats as
Gregorian-date diary entries, except that the date must be preceded with
an @samp{H} for Hebrew dates and an @samp{I} for Islamic dates.
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

@smallexample
HHeshvan 25 Happy Hebrew birthday!
@end smallexample

@noindent
and would appear in the diary for any date that corresponds to Heshvan 25
on the Hebrew calendar.  Similarly, an Islamic-date diary entry might be

@smallexample
IDhu al-Qada 25 Happy Islamic birthday!
@end smallexample

@noindent
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 (@samp{&}).

  There are commands to help you in making Hebrew- and Islamic-date
entries to your diary:

@table @kbd
@item i h d
Add a diary entry for the Hebrew date corresponding to the selected date
(@code{insert-hebrew-diary-entry}).
@item i h m
Add a diary entry for the day of the Hebrew month corresponding to the
selected date (@code{insert-monthly-hebrew-diary-entry}).
@item i h y
Add a diary entry for the day of the Hebrew year corresponding to the
selected date (@code{insert-yearly-hebrew-diary-entry}).
@item i i d
Add a diary entry for the Islamic date corresponding to the selected date
(@code{insert-islamic-diary-entry}).
@item i i m
Add a diary entry for the day of the Islamic month corresponding to the
selected date (@code{insert-monthly-islamic-diary-entry}).
@item i i y
Add a diary entry for the day of the Islamic year corresponding to the
selected date (@code{insert-yearly-islamic-diary-entry}).
@end table

@findex insert-hebrew-diary-entry
@findex insert-monthly-hebrew-diary-entry
@findex insert-yearly-hebrew-diary-entry
@findex insert-islamic-diary-entry
@findex insert-monthly-islamic-diary-entry
@findex insert-yearly-islamic-diary-entry
  These commands work exactly like the corresponding commands for ordinary
diary entries: Move point to a date in the calendar window and the above
commands insert the Hebrew or Islamic date (corresponding to the date
indicated by point) at the end of your diary file and you can then type the
diary entry.  If you want the diary entry to be nonmarking, give a numeric
argument to the command.

@node Fancy Diary Display
@section Fancy Diary Display
@vindex diary-display-hook
@findex simple-diary-display

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

@cindex diary buffer
@findex fancy-diary-display
@example
(add-hook 'diary-display-hook 'fancy-diary-display)
@end example

@noindent
then fancy mode displays diary entries and holidays by copying them into
a special buffer that exists only for display.  Copying 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 @code{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
@kbd{7 d} and then do @kbd{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 @code{holidays-in-diary-buffer} to
@code{nil}.

@vindex diary-list-include-blanks
  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
@code{diary-list-include-blanks} to @code{t}.@refill

@cindex sorting diary entries
  If you use the fancy diary display, you can use the normal hook
@code{list-diary-entries-hook} to sort each day's diary entries by their
time of day.  Add this line to your @file{.emacs} file:

@findex sort-diary-entries
@example
(add-hook 'list-diary-entries-hook 'sort-diary-entries)
@end example

@noindent
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.

@node Included Diary Files
@section Included Diary Files

  If you use the fancy diary display, you can have diary entries from other
files included with your own by an ``include'' mechanism.  This facility makes
possible the sharing of common diary files among groups of users.  Lines in
the diary file of this form:

@smallexample
#include "@var{filename}"
@end smallexample

@noindent
includes the diary entries from the file @var{filename} in the fancy
diary buffer (because the ordinary diary buffer is just the buffer
associated with your diary file, you cannot use the include mechanism
unless you use the fancy diary buffer).  The include mechanism is
recursive, by the way, so that included files can include other files,
and so on; you must be careful not to have a cycle of inclusions, of
course.  To enable the include facility, add lines as follows to your
@file{.emacs} file:

@vindex list-diary-entries-hook
@vindex mark-diary-entries-hook
@findex include-other-diary-files
@findex mark-included-diary-files
@smallexample
(add-hook 'list-diary-entries-hook 'include-other-diary-files)
(add-hook 'mark-diary-entries-hook 'mark-included-diary-files)
@end smallexample

@node Sexp Diary Entries
@section Sexp Entries and the Fancy Diary Display
@cindex sexp diary entries

  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 @samp{%d} in this dairy entry:

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

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

@smallexample
Arthur's birthday (42 years old)
@end smallexample

@noindent
If the diary file instead contains this entry:

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

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

@smallexample
Arthur's 42nd birthday
@end smallexample

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

@findex diary-cyclic
@smallexample
%%(diary-cyclic 50 1 1 1990) Renew medication (%d%s time)
@end smallexample

@noindent
looks like this:

@smallexample
Renew medication (5th time)
@end smallexample

@noindent
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.  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

@smallexample
&%%(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
@end smallexample

@noindent
applies to just those dates.  This example illustrates how the sexp can
depend on the variable @code{date}; this variable is a list (@var{month}
@var{day} @var{year}) that gives the Gregorian date for which the diary
entries are being found.  If the value of the expression is @code{t},
the entry applies to that date.  If the expression evaluates to
@code{nil}, the entry does @emph{not} apply to that date.

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

@findex diary-sunrise-sunset
@findex diary-phases-of-moon
@findex diary-day-of-year
@findex diary-iso-date
@findex diary-julian-date
@findex diary-astro-day-number
@findex diary-hebrew-date
@findex diary-islamic-date
@findex diary-french-date
@findex diary-mayan-date
@table @code
@item %%(diary-sunrise-sunset)
Make a diary entry for the local times of today's sunrise and sunset.
@item %%(diary-phases-of-moon)
Make a diary entry for the phases (quarters) of the moon.
@item %%(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.
@item %%(diary-iso-date)
Make a diary entry with today's equivalent ISO commercial date.
@item %%(diary-julian-date)
Make a diary entry with today's equivalent date on the Julian calendar.
@item %%(diary-astro-day-number)
Make a diary entry with today's equivalent astronomical (Julian) day number.
@item %%(diary-hebrew-date)
Make a diary entry with today's equivalent date on the Hebrew calendar.
@item %%(diary-islamic-date)
Make a diary entry with today's equivalent date on the Islamic calendar.
@item %%(diary-french-date)
Make a diary entry with today's equivalent date on the French Revolutionary
calendar.
@item %%(diary-mayan-date)
Make a diary entry with today's equivalent date on the Mayan calendar.
@end table

@noindent
Thus including the diary entry

@smallexample
&%%(diary-hebrew-date)
@end smallexample

@noindent
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 @samp{&%%(diary-hebrew-date)} appears in the
diary for any date, but does nothing particularly useful.)

  There are a number of other available sexp diary entries that are important
to those who follow the Hebrew calendar:

@cindex rosh hodesh
@findex diary-rosh-hodesh
@cindex parasha, weekly
@findex diary-parasha
@cindex candle lighting times
@findex diary-sabbath-candles
@cindex omer count
@findex diary-omer
@cindex yahrzeits
@findex diary-yahrzeit
@table @code
@item %%(diary-rosh-hodesh)
Make a diary entry that tells the occurrence and ritual announcement of each
new Hebrew month.
@item %%(diary-parasha)
Make a Saturday diary entry that tells the weekly synagogue scripture reading.
@item %%(diary-sabbath-candles)
Make a Friday diary entry that tells the @emph{local time} of Sabbath
candle lighting.
@item %%(diary-omer)
Make a diary entry that gives the omer count, when appropriate.
@item %%(diary-yahrzeit @var{month} @var{day} @var{year}) @var{name}
Make a diary entry marking the anniversary of a date of death.  The date
is the @emph{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 @var{day},
@var{month}, @var{year}.)
@end table

@node Appt Customizing
@section Customizing Appointment Reminders

  You can specify exactly how Emacs reminds you of an appointment and
how far in advance it begins doing so.  Here are the variables that you
can set:

@vindex appt-message-warning-time
@vindex appt-audible
@vindex appt-visible
@vindex appt-display-mode-line
@vindex appt-msg-window
@vindex appt-display-duration
@table @code
@item appt-message-warning-time
The time in minutes before an appointment that the reminder begins.  The
default is 10 minutes.
@item appt-audible
If this is @code{t} (the default), Emacs rings the terminal bell for
appointment reminders.
@item appt-visible
If this is @code{t} (the default), Emacs displays the appointment
message in echo area.
@item appt-display-mode-line
If this is @code{t} (the default), Emacs displays the number of minutes
to the appointment on the mode line.
@item appt-msg-window
If this is @code{t} (the default), Emacs displays the appointment
message in another window.
@item appt-display-duration
The number of seconds an appointment message is displayed.  The default
is 5 seconds.
@end table