@c This is part of the Emacs manual.
@c Copyright (C) 1985, 1986, 1987, 1993 Free Software Foundation, Inc.
@c See file emacs.texi for copying conditions.
@node Calendar/Diary, GNUS, Dired, Top
@chapter The Calendar and the Diary
@cindex calendar
@findex calendar

  Emacs provides the functions of a desk calendar, with a diary of
planned or past events.  To enter the calendar, type @kbd{M-x calendar};
this displays a three-month calendar centered on the current month, with
point on the current date.  If you use prefix argument as in @kbd{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 and the
major mode is Calendar mode.

  To exit the calendar, type @kbd{q}.

@menu
* Calendar Motion::       Moving through the calendar; selecting a date.
* Scroll Calendar::       Bringing earlier or later months onto the screen.
* Counting Days::         How many days are there between two dates?
* General Calendar::      Exiting or recomputing the calendar.
* Holidays::              Displaying dates of holidays.
* Sunrise/Sunset::        Displaying local times of sunrise and sunset.
* Lunar Phases::          Displaying phases of the moon.
* Other Calendars::       Converting dates to other calendar systems.
* Diary::                 Displaying events from your diary.
* Appointments::	  Reminders when it's time to do something.
* Daylight Savings::      How to specify when daylight savings time is active.
@end menu

@node Calendar Motion
@section Movement in the Calendar

  Calendar mode lets you move 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.  Moving to a date lets you view its holidays or diary entries,
convert it to other calendars; moving longer time periods is useful
simply to scroll the calendar.

@menu
* Calendar Unit Motion::       Moving by days, weeks, months, and years.
* Move to Beginning or End::   Moving to start/end of weeks, months, and years.
* Specified Dates::            Moving to the current date or another specific date.
@end menu

@node Calendar Unit Motion
@subsection 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.

@table @kbd
@item C-f
Move point one day forward (@code{calendar-forward-day}).
@item C-b
Move point one day backward (@code{calendar-backward-day}).
@item C-n
Move point one week forward (@code{calendar-forward-week}).
@item C-p
Move point one week backward (@code{calendar-backward-week}).
@item M-@}
Move point one month forward (@code{calendar-forward-month}).
@item M-@{
Move point one month backward (@code{calendar-backward-month}).
@item C-x ]
Move point one year forward (@code{calendar-forward-year}).
@item C-x [
Move point one year backward (@code{calendar-forward-year}).
@end table

@kindex C-f @r{(Calendar mode)}
@findex calendar-forward-day
@kindex C-b @r{(Calendar mode)}
@findex calendar-backward-day
@kindex C-n @r{(Calendar mode)}
@findex calendar-forward-week
@kindex C-p @r{(Calendar mode)}
@findex calendar-backward-week
  The day and week commands are natural analogues of the usual Emacs
commands for moving by characters and by lines.  Just as @kbd{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 @kbd{C-p}
moves to the same day in the previous week.

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

@kindex M-@} @r{(Calendar mode)}
@findex calendar-forward-month
@kindex M-@{ @r{(Calendar mode)}
@findex calendar-backward-month
@kindex C-x ] @r{(Calendar mode)}
@findex calendar-forward-year
@kindex C-x [ @r{(Calendar mode)}
@findex calendar-forward-year
  The commands for motion by months and years work like those for
weeks, but move a larger distance.  The month commands @kbd{M-@}} and
@kbd{M-@{} move forward or backward by an entire month's time.  The
year commands @kbd{C-x ]} and @kbd{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,
@kbd{100 C-f} moves point 100 days forward from its present location.

@node Move to Beginning or End
@subsection Beginning or End of Week, Month or Year

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

@table @kbd
@kindex C-a @r{(Calendar mode)}
@findex calendar-beginning-of-week
@item C-a
Move point to beginning of week (@code{calendar-beginning-of-week}).
@kindex C-e @r{(Calendar mode)}
@findex calendar-end-of-week
@item C-e
Move point to end of week (@code{calendar-end-of-week}).
@kindex M-a @r{(Calendar mode)}
@findex calendar-beginning-of-month
@item M-a
Move point to beginning of month (@code{calendar-beginning-of-month}).
@kindex M-e @r{(Calendar mode)}
@findex calendar-end-of-month
@item M-e
Move point to end of month (@code{calendar-end-of-month}).
@kindex M-< @r{(Calendar mode)}
@findex calendar-beginning-of-year
@item M-<
Move point to beginning of year (@code{calendar-beginning-of-year}).
@kindex M-> @r{(Calendar mode)}
@findex calendar-end-of-year
@item M->
Move point to end of year (@code{calendar-end-of-year}).
@end table

  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.

@node Specified Dates
@subsection Particular Dates

  Calendar mode provides commands for getting to a particular date
specified absolutely.

@table @kbd
@item g d
Move point to specified date (@code{calendar-goto-date}).
@item o
Center calendar around specified month (@code{calendar-other-month}).
@item .
Move point to today's date (@code{calendar-current-month}).
@end table

@kindex g d @r{(Calendar mode)}
@findex calendar-goto-date
  @kbd{g d} (@code{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 @samp{1990}, not @samp{90}.

@kindex o @r{(Calendar mode)}
@findex calendar-other-month
  @kbd{o} (@code{calendar-other-month}) prompts for a month and year,
then centers the three-month calendar around that month.

@kindex . @r{(Calendar mode)}
@findex calendar-current-month
  You can return to today's date with @kbd{.}
(@code{calendar-current-month}).

@node Scroll Calendar
@section Scrolling in the Calendar

  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.

@table @kbd
@item C-x <
Scroll calendar one month forward (@code{scroll-calendar-left}).
@item C-x >
Scroll calendar one month backward (@code{scroll-calendar-right}).
@item C-v
@itemx @key{NEXT}
Scroll calendar three months forward
(@code{scroll-calendar-left-three-months}).
@item M-v
@itemx @key{PRIOR}
Scroll calendar three months backward
(@code{scroll-calendar-right-three-months}).
@item SPC
Scroll the next window (@code{scroll-other-window}).
@end table

@kindex C-x < @r{(Calendar mode)}
@findex scroll-calendar-left
@kindex C-x > @r{(Calendar mode)}
@findex scroll-calendar-right
  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.  @kbd{C-x <} scrolls
the calendar contents one month to the left; that is, it moves the
display forward in time.  @kbd{C-x >} scrolls the contents to the
right, which moves backwards in time.

@kindex C-v @r{(Calendar mode)}
@findex scroll-calendar-left-three-months
@kindex M-v @r{(Calendar mode)}
@findex scroll-calendar-right-three-months
  The commands @kbd{C-v} and @kbd{M-v} scroll the calendar by an entire
``screenful''---three months---in analogy with the usual meaning of these
commands.  @kbd{C-v} makes later dates visible and @kbd{M-v} makes earlier
dates visible.  These commands take a numeric argument as a repeat
count; in particular, since @kbd{C-u} (@code{universal-argument}) multiplies
the next command by four, typing @kbd{C-u C-v} scrolls the calendar forward by
a year and typing @kbd{C-u M-v} scrolls the calendar backward by a year.

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

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

@node Counting Days
@section Counting Days

@table @kbd
@item M-=
Display the number of days in the current region
(@code{calendar-count-days-region}).
@end table

@kindex M-= @r{(Calendar mode)}
@findex calendar-count-days-region
  To determine the number of days in the region, type @kbd{M-=}
(@code{calendar-count-days-region}).  The numbers of days printed is
@emph{inclusive}; that is, it includes the days specified by mark and
point.

@node General Calendar
@section Miscellaneous Calendar Commands

@table @kbd
@item p d
Display day-in-year (@code{calendar-print-day-of-year}).
@item C-c C-l
Regenerate the calendar window (@code{redraw-calendar}).
@item q
Exit from calendar (@code{exit-calendar}).
@end table

@kindex p d @r{(Calendar mode)}
@cindex day of year
@findex calendar-print-day-of-year
  To print the number of days elapsed since the start of the year, or
the number of days remaining in the year, type the @kbd{p d} command
(@code{calendar-print-day-of-year}).  This displays both of those
numbers in the echo area.  The number of days elapsed includes the
selected date.  The number of days remaining does not include that
date.

@kindex C-c C-l @r{(Calendar mode)}
@findex redraw-calendar
  If the calendar window gets corrupted, type @kbd{C-c C-l}
(@code{redraw-calendar}) to redraw it.

@kindex q @r{(Calendar mode)}
@findex exit-calendar
  To exit from the calendar, type @kbd{q} (@code{exit-calendar}).  This
buries all buffers related to the calendar and returns the window display
to what it was when you entered the calendar.

@node Holidays
@section Holidays
@cindex holidays

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

@table @kbd
@item h
Display holidays for the selected date
(@code{calendar-cursor-holidays}).
@item x
Mark holidays in the calendar window (@code{mark-calendar-holidays}).
@item u
Unmark calendar window (@code{calendar-unmark}).
@item a
List all holidays for the displayed three months in another window
(@code{list-calendar-holidays}).
@item M-x holidays
List all holidays for three months around today's date in another
window.
@end table

@kindex h @r{(Calendar mode)}
@findex calendar-cursor-holidays
  To see if any holidays fall on a given date, position point on that
date in the calendar window and use the @kbd{h} command.  This names
the holidays for that date, in the echo area if they fit there, 
otherwise in a separate window.

@kindex x @r{(Calendar mode)}
@findex mark-calendar-holidays
@kindex u @r{(Calendar mode)}
@findex calendar-unmark
  To find the distribution of holidays for a wider period, use the
@kbd{x} command.  This displays a @samp{*} after each date on which a
holiday falls.  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 @kbd{u}, which also
erases any diary marks (@pxref{Diary}).

@kindex a @r{(Calendar mode)}
@findex list-calendar-holidays
  To get even more detailed information, use the @kbd{a} command, which
displays a separate buffer containing a list of all holidays in the
current three-month range.

@findex holidays
  The command @kbd{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 @kbd{C-u M-x holidays}, which
prompts for the month and year.

@c ??? Delete mention of floating point?
  The holidays known to Emacs include American holidays and the major
Christian, Jewish, and Islamic holidays; when floating point is
available, the calendar also knows about solstices and equinoxes.

  The dates used by Emacs for holidays are based on @emph{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 American law mandates that daylight savings time
begins on the first Sunday in April.  Emacs always uses this definition,
even though it is wrong for some prior years.

@node Sunrise/Sunset
@section Times of Sunrise and Sunset
@cindex sunrise and sunset

@c ??? Delete mention of floating point?
  Emacs can tell you, to within a minute or two, the times of sunrise and
sunset for any date, if floating point is available.

@table @kbd
@item S
Display times of sunrise and sunset for the selected date
(@code{calendar-sunrise-sunset}).
@item M-x sunrise-sunset
Display times of sunrise and sunset for today's date.
@item C-u M-x sunrise-sunset
Display times of sunrise and sunset for a specified date.
@end table

@kindex S @r{(Calendar mode)}
@findex calendar-sunrise-sunset
@findex sunrise-sunset
  Within the calendar, to display the @emph{local times} of sunrise and
sunset in the echo area, move point to the date you want, and type
@kbd{S}.

  The command @kbd{M-x sunrise-sunset} is available outside the
calendar to print this information for today's date or a specified
date.  To specify a date other than today, use @kbd{C-u M-x
sunrise-sunset}, which prompts for the year, month, and day.

  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:

@vindex calendar-location-name
@vindex calendar-longitude
@vindex calendar-latitude
@example
(setq calendar-latitude 40.1)
(setq calendar-longitude -88.2)
(setq calendar-location-name "Urbana, IL")
@end example

@noindent
Use one decimal place in the values of @code{calendar-latitude} and
@code{calendar-longitude}.

  Your time zone also affects the local time of sunrise and sunset.
Emacs usually gets this 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:

@vindex calendar-time-zone
@vindex calendar-standard-time-zone-name
@vindex calendar-daylight-time-zone-name
@example
(setq calendar-time-zone -360)
(setq calendar-standard-time-zone-name "CST")
(setq calendar-daylight-time-zone-name "CDT")
@end example

@noindent
The value of @code{calendar-time-zone} is the number of minutes
difference between your local standard time and Universal Time
(Greenwich time).  The values of @code{calendar-standard-time-zone-name}
and @code{calendar-daylight-time-zone-name} are the abbreviations used
in your time zone.

  Emacs displays the times of sunrise and sunset @emph{corrected for
daylight savings time}.  The default rule for the starting and stopping
dates of daylight savings time is the American rule.  @xref{Daylight
Savings}, for how to specify a different rule.

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

@node Lunar Phases
@section Phases of the Moon
@cindex phases of the moon
@cindex moon, phases of

@c ??? Delete mention of floating point?
  Emacs can tell you the dates and times of the phases of the moon (new
moon, first quarter, full moon, last quarter), if floating point is
available.  This feature is useful for debugging problems that ``depend
on the phase of the moon.''

@table @kbd
@item M
Display the dates and times for all the quarters of the moon for the
three-month period shown (@code{calendar-phases-of-moon}).
@item M-x phases-of-moon
Display dates and times of the quarters of the moon for three months around
today's date.
@end table

@kindex M @r{(Calendar mode)}
@findex calendar-phases-of-moon
  Within the calendar, use the @kbd{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.

@findex phases-of-moon
  Outside the calendar, use the command @kbd{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 @kbd{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 @code{calendar-time-zone} is void, Universal Time (the
Greenwich time zone) is used.  @xref{Daylight Savings}.

@node Other Calendars
@section Conversion To and From Other Calendars

@cindex Gregorian calendar
  The Emacs calendar displayed is @emph{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.

@menu
* Calendar Systems::	  The calendars Emacs understands
			    (aside from Gregorian).
* To Other Calendar::     Converting the selected date to various calendars.
* From Other Calendar::   Moving to a date specified in another calendar.
* Mayan Calendar::	  Moving to a date specified in a Mayan calendar.
@end menu

@node Calendar Systems
@subsection Supported Calendar Systems

@cindex ISO commercial calendar
  The ISO commercial calendar is used largely in Europe.

@cindex Julian calendar
  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.

@cindex Julian day numbers
@cindex astronomical day numbers
  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 @emph{Julian day number} or the @emph{Astronomical day number}.

@cindex Hebrew calendar
  The Hebrew calendar is the one used to determine the dates of Jewish
holidays.  Hebrew calendar dates begin and end at sunset.

@cindex Islamic calendar
  The Islamic (Moslem) calendar is the one used to determine the dates
of Moslem 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 occurrence can vary slightly from the dates computed by
Emacs.  Islamic calendar dates begin and end at sunset.

@cindex French Revolutionary calendar
  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.

@cindex Mayan calendar
  The Maya of Central America used three separate, overlapping calendar
systems, the @emph{long count}, the @emph{tzolkin}, and the @emph{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.

@node To Other Calendar
@subsection Converting To Other Calendars

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

@table @kbd
@kindex p @r{(Calendar mode)}
@findex calendar-print-iso-date
@item p c
Display ISO commercial calendar equivalent for selected day
(@code{calendar-print-iso-date}).
@findex calendar-print-julian-date
@item p j
Display Julian date for selected day (@code{calendar-print-julian-date}).
@findex calendar-print-astro-day-number
@item p a
Display astronomical (Julian) day number for selected day
(@code{calendar-print-astro-day-number}).
@findex calendar-print-hebrew-date
@item p h
Display Hebrew date for selected day (@code{calendar-print-hebrew-date}).
@findex calendar-print-islamic-date
@item p i
Display Islamic date for selected day (@code{calendar-print-islamic-date}).
@findex calendar-print-french-date
@item p f
Display French Revolutionary date for selected day
(@code{calendar-print-french-date}).
@findex calendar-print-mayan-date
@item p m
Display Mayan date for selected day (@code{calendar-print-mayan-date}).
@end table

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

@node From Other Calendar
@subsection Converting From Other Calendars

  You can move to dates that you specify on the Commercial, Julian,
astronomical, Hebrew, Islamic, or French calendars:

@kindex g @var{char} @r{(Calendar mode)}
@findex calendar-goto-iso-date
@findex calendar-goto-julian-date
@findex calendar-goto-astro-day-number
@findex calendar-goto-hebrew-date
@findex calendar-goto-islamic-date
@findex calendar-goto-french-date
@table @kbd
@item g c
Move to a date specified in the ISO commercial calendar
(@code{calendar-goto-iso-date}).
@item g j
Move to a date specified in the Julian calendar
(@code{calendar-goto-julian-date}).
@item g a
Move to a date specified in astronomical (Julian) day number
(@code{calendar-goto-astro-day-number}).
@item g h
Move to a date specified in the Hebrew calendar
(@code{calendar-goto-hebrew-date}).
@item g i
Move to a date specified in the Islamic calendar
(@code{calendar-goto-islamic-date}).
@item g f
Move to a date specified in the French Revolutionary calendar
(@code{calendar-goto-french-date}).
@end table

  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
(@pxref{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.

@findex list-yahrzeit-dates
@cindex yahrzeits
  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 @kbd{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.

@node Mayan Calendar
@subsection Converting from the Mayan Calendar

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

@table @kbd
@item g m l
Move to a date specified by the long count calendar
(@code{calendar-goto-mayan-long-count-date}).
@item g m p t
Move to the previous occurrence of a place in the
tzolkin calendar (@code{calendar-previous-tzolkin-date}).
@item g m n t
Move to the next occurrence of a place in the
tzolkin calendar (@code{calendar-next-tzolkin-date}).
@item g m p h
Move to the previous occurrence of a place in the
haab calendar (@code{calendar-previous-haab-date}).
@item g m n h
Move to the next occurrence of a place in the
haab calendar (@code{calendar-next-haab-date}).
@item g m p c
Move to the previous occurrence of a place in the
calendar round (@code{calendar-previous-calendar-round-date}).
@item g m n c
Move to the next occurrence of a place in the
calendar round (@code{calendar-next-calendar-round-date}).
@end table

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

@display
1 kin = 1 day@ @ @ 1 uinal = 20 kin@ @ @ 1 tun = 18 uinal
1 katun = 20 tun@ @ @ 1 baktun = 20 katun
@end display

@kindex g m @r{(Calendar mode)}
@findex calendar-goto-mayan-long-count-date
@noindent
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
@kbd{g m l} command, type the Mayan long count date with the baktun,
katun, tun, uinal, and kin separated by periods.

@findex calendar-previous-tzolkin-date
@findex calendar-next-tzolkin-date
@cindex Mayan tzolkin calendar
  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 @kbd{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 @kbd{g m n t}
to go to the next occurrence of a tzolkin date.

@findex calendar-previous-haab-date
@findex calendar-next-haab-date
@cindex Mayan haab calendar
  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
@kbd{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 @kbd{g m n h} to go to the next occurrence of a haab
date.

@findex calendar-previous-calendar-round-date
@findex calendar-next-calendar-round-date
@cindex Mayan calendar round
  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
@emph{calendar round}.  If you type @kbd{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 @kbd{g m p c} to move point to the
next occurrence of a combination.  Emacs signals an error if the
haab/tzolkin date you have typed is impossible.

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

@node Diary
@section The Diary
@cindex 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 @dfn{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 @file{~/diary} as the diary file.  This is the
same file that the @code{calendar} utility uses.  A sample
@file{~/diary} file is:

@example
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.
@end example

  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.

@menu
* Diary Commands::         Viewing diary entries and associated calendar dates.
* Format of Diary File::   Entering events in your diary.
* Date Formats::	   Various ways you can specify dates.
* Adding to Diary::	   Commands to create diary entries.
* Special Diary Entries::  Anniversaries, blocks of dates, cyclic entries, etc.
@end menu

@node Diary Commands
@subsection Commands Displaying Diary Entries

  Once you have created a @file{~/diary} file, you can view it from
within the calendar.  You can also view today's events outside of
Calendar mode.

@table @kbd
@item d
Display any diary entries for the selected date
(@code{view-diary-entries}).
@item s
Display entire diary file (@code{show-all-diary-entries}).
@item m
Mark all visible dates that have diary entries
(@code{mark-diary-entries}).
@item u
Unmark calendar window (@code{calendar-unmark}).
@item M-x print-diary-entries
Print hard copy of the diary display as it appears.
@item M-x diary
Display any diary entries for today's date.
@end table

@kindex d @r{(Calendar mode)}
@findex view-diary-entries
  Displaying the diary entries with @kbd{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 @kbd{d}, it shows all the diary
entries for that many successive days.  Thus, @kbd{2 d} displays all the
entries for the selected date and for the following day.

@kindex m @r{(Calendar mode)}
@findex mark-diary-entries
  To get a broader view of which days are mentioned in the diary, use
the @kbd{m} command.  This places a @samp{+} after each date which has a
diary entry.  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 @kbd{u}, which also
turns off holiday marks (@pxref{Holidays}).

@kindex s @r{(Calendar mode)}
@findex show-all-diary-entries
  To see the full diary file, rather than just some of the entries, use
the @kbd{s} command.

  Display of selected diary entries uses the selective display feature
to hide entries that don't apply.  This is the same feature that Outline
mode uses to show part of an outline (@pxref{Outline Mode}).  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
@emph{as it appears}; this command is @kbd{M-x print-diary-entries}.  It
sends the data directly to the printer.  You can customize it like
@code{lpr-region} (@pxref{Hardcopy}).

@findex diary
  The command @kbd{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 @code{number-of-diary-entries} specifies
how many days to include.  @xref{Calendar/Diary Options,, Calendar/Diary
Options, elisp, The Emacs Lisp Reference Manual}.

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

@node Format of Diary File
@subsection The Diary File
@cindex diary file

@vindex diary-file
  Your @dfn{diary file} is a file that records events associated with
particular dates.  The name of the diary file is specified by the variable
@code{diary-file}; @file{~/diary} is the default.  You can use the same file
for the @code{calendar} utility program, since its formats are a subset of the
ones allowed by the Emacs diary facilities.

  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 (@samp{&}) 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:

@example
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
@end example

@noindent
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 @emph{entire}
diary file, with portions of it concealed from view.  This means, for
instance, that the @kbd{C-f} (@code{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.

  @emph{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 @kbd{s} (@code{show-all-diary-entries}).

@node Date Formats
@subsection 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.

@example
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
@end example

  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
@samp{@var{month}/@var{day}} or
@samp{@var{month}/@var{day}/@var{year}}.  This must be followed by a
nondigit.  In the date itself, @var{month} and @var{day} are numbers of
one or two digits.  @var{year} is a number and may be abbreviated to the
last two digits; that is, you can use @samp{11/12/1989} or
@samp{11/12/89}.

  Dates can also have the form @samp{@var{monthname} @var{day}} or
@samp{@var{monthname} @var{day}, @var{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 @dfn{generic}, or 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,
@var{month}, @var{day}, or @var{year} can be a @samp{*}; this matches
any month, day, or year, respectively.  Thus, a diary entry @samp{3/*/*}
matches any day in March of any year; so does @samp{march *}.

@vindex european-calendar-style
@findex european-calendar
@findex american-calendar
  If you prefer the European style of writing dates---in which the day
comes before the month---type @kbd{M-x european-calendar} while in the
calendar, or set the variable @code{european-calendar-style} to @code{t}
@emph{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 @var{monthname} in the European style.)  To go back to the (default)
American style of writing dates, type @kbd{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.

@node Adding to Diary
@subsection Commands to Add to the Diary

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

@table @kbd
@item i d
Add a diary entry for the selected date (@code{insert-diary-entry}).
@item i w
Add a diary entry for the selected day of the week (@code{insert-weekly-diary-entry}).
@item i m
Add a diary entry for the selected day of the month (@code{insert-monthly-diary-entry}).
@item i y
Add a diary entry for the selected day of the year (@code{insert-yearly-diary-entry}).
@end table

@kindex i d @r{(Calendar mode)}
@findex insert-diary-entry
  You can make a diary entry for a specific date by selecting that date
in the calendar window and typing the @kbd{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.

@kindex i w @r{(Calendar mode)}
@findex insert-weekly-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
@kbd{i w}.  This inserts the day-of-week as a generic date; you can then
type the rest of the diary entry.

@kindex i m @r{(Calendar mode)}
@findex insert-monthly-diary-entry
@kindex i y @r{(Calendar mode)}
@findex insert-yearly-diary-entry
  You can make a monthly diary entry in the same fashion.  Select the
day of the month, use the @kbd{i m} command, and type rest of the
entry.  Similarly, you can insert a yearly diary entry with the @kbd{i
y} command.

  All of the above commands make marking diary entries.  If you want the
diary entry to be nonmarking, give a prefix argument to the command.
For example, @kbd{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.

@node Special Diary Entries
@subsection Special Diary Entries

  In addition to entries based on calendar dates, your diary file can
contain @dfn{special 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 special entry contains
@samp{%%} 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
special entries:

@table @kbd
@item i a
Add an anniversary diary entry for the selected date
(@code{insert-anniversary-diary-entry}).
@item i b
Add a block diary entry for the current region
(@code{insert-block-diary-entry}).
@item i c
Add a cyclic diary entry starting at the date
(@code{insert-cyclic-diary-entry}).
@end table

@kindex i a @r{(Calendar mode)}
@findex insert-anniversary-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 @kbd{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:

@findex diary-anniversary
@example
%%(diary-anniversary 10 31 1948) Arthur's birthday
@end example

@noindent
This entry applies to October 31 in any year after 1948; @samp{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.

@kindex i b @r{(Calendar mode)}
@findex insert-block-diary-entry
  You can make a diary entry entry for a block of dates by setting the
mark at the date at one end of the block, moving point to the date at
the other end of the block, and using the @kbd{i b} command.  This
command causes the end of your diary file to be displayed in another
window and the block description to be inserted; you can then type the
diary entry.  Here is a block diary entry that applies to all dates from
June 24, 1990 through July 10, 1990:

@findex diary-block
@example
%%(diary-block 6 24 1990 7 10 1990) Vacation
@end example

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

@kindex i c @r{(Calendar mode)}
@findex insert-cyclic-diary-entry
   @dfn{Cyclic} diary entries repeat after a fixed interval of days.  To
create one, select the starting date and use the @kbd{i c} command.  The
command prompts for the length of interval, then inserts the entry.
It looks like this:

@findex diary-cyclic
@example
%%(diary-cyclic 50 3 1 1990) Renew medication
@end example

@noindent
which applies to March 1, 1990 and every 50th day following; @samp{3 1 1990}
specifies the starting date.  (If you are using the European calendar style,
the month and day are interchanged.)

  All three of the these commands make marking diary entries.  If you want the
diary entry to be nonmarking, give a numeric argument to the command.  For
example, @kbd{C-u i a} makes a nonmarking anniversary diary
entry.

  Marking sexp diary entries in the calendar is @emph{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 @samp{&}) when possible.

  Another sophisticated kind of sexp entry, a @dfn{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 @code{cron} utility.  Here is a nonmarking, floating diary entry
that applies to the last Thursday in November:

@findex diary-float
@example
&%%(diary-float 11 4 -1) American Thanksgiving
@end example

@noindent
The 11 specifies November (the eleventh month), the 4 specifies Thursday
(the fourth day of the week, where Sunday is numbered zero), and the
@minus{}1 specifies ``last'' (1 would mean ``first'', 2 would mean
``second'', @minus{}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 @samp{'(1 2 3)} and have the entry apply to the last
Thursday of January, February, and March.  If the month is @code{t}, the
entry applies to all months of the year.@refill

  Most generally, special diary entries can perform arbitrary
computations to determine when they apply.  @xref{Sexp Diary Entries,,
Sexp Diary Entries, elisp, The Emacs Lisp Reference Manual}.

@node Appointments
@section Appointments
@cindex appointment notification

  If you have a diary entry for an appointment, and that diary entry
begins with a recognizable time of day, Emacs can warn you, several
minutes beforehand, that that appointment is pending.  Emacs alerts you
to the appointment by displaying a message in the mode line.

@vindex diary-display-hook
@findex appt-make-list
  To enable appointment notification, you must enable the time display
feature of Emacs, @kbd{M-x display-time} (@pxref{Mode Line}).  You must
also add the function @code{appt-make-list} to the
@code{diary-display-hook}, like this:

@example
(add-hook 'diary-display-hook 'appt-make-list)
@end example

  With these preparations done, when you display the diary (either with
the @kbd{d} command in the calendar window or with the @kbd{M-x diary}
command), it sets up an appointment list of all the diary entries found
with recognizable times of day, and reminds you just before each of
them.

  For example, if you the diary file contains these lines:

@example
Monday
  9:30am Coffee break
 12:00pm Lunch        
@end example

@noindent
Then on Mondays, after you have displayed the diary, you will be
reminded at 9:20am about your coffee break and at 11:50am about lunch.

  Diary entries can have the time in the conventional American style, or
in ``military'' style.  You need not be consistent; your diary file can
have a mixture of the two styles.

@vindex appt-display-diary
  Emacs updates the appointments list automatically just after
midnight.  This also displays the next days' diary entries in the diary
buffer, unless you set @code{appt-display-diary} to @code{nil}.

@findex appt-add
@findex appt-delete
@cindex alarm clock
  You can also use the appointment notification facility like an alarm
clock.  The command @kbd{M-x appt-add} adds entries to the appointment
list without affecting your diary file.  You delete entries from the
appointment list with @kbd{M-x appt-delete}.

@vindex appt-issue-message
  You can turn off the appointment notification feature at any time by
setting @code{appt-issue-message} to @code{nil}.

@node Daylight Savings
@section Daylight Savings Time
@cindex daylight savings time
@vindex calendar-daylight-savings-starts
@vindex calendar-daylight-savings-ends

  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
default starting and stopping dates for daylight savings time are the
present-day American rules of the first Sunday in April until the last
Sunday in October, but you can specify whatever rules you want by
setting @code{calendar-daylight-savings-starts} and
@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})}.

  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 default value of @code{calendar-daylight-savings-starts} is this,

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

@noindent
which computes the first 0th day (Sunday) of the fourth month (April) in
the year specified by @code{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

  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}.
