cpython/Doc/library/calendar.rst

:mod:`calendar` --- General calendar-related functions
======================================================

.. module:: calendar
   :synopsis: Functions for working with calendars, including some emulation
              of the Unix cal program.

.. sectionauthor:: Drew Csillag <drew_csillag@geocities.com>

**Source code:** :source:`Lib/calendar.py`

--------------

This module allows you to output calendars like the Unix :program:`cal` program,
and provides additional useful functions related to the calendar. By default,
these calendars have Monday as the first day of the week, and Sunday as the last
(the European convention). Use :func:`setfirstweekday` to set the first day of
the week to Sunday (6) or to any other weekday.  Parameters that specify dates
are given as integers. For related
functionality, see also the :mod:`datetime` and :mod:`time` modules.

The functions and classes defined in this module
use an idealized calendar, the current Gregorian calendar extended indefinitely
in both directions.  This matches the definition of the "proleptic Gregorian"
calendar in Dershowitz and Reingold's book "Calendrical Calculations", where
it's the base calendar for all computations.  Zero and negative years are
interpreted as prescribed by the ISO 8601 standard.  Year 0 is 1 BC, year -1 is
2 BC, and so on.


.. class:: Calendar(firstweekday=0)

   Creates a :class:`Calendar` object. *firstweekday* is an integer specifying the
   first day of the week. ``0`` is Monday (the default), ``6`` is Sunday.

   A :class:`Calendar` object provides several methods that can be used for
   preparing the calendar data for formatting. This class doesn't do any formatting
   itself. This is the job of subclasses.


   :class:`Calendar` instances have the following methods:

   .. method:: iterweekdays()

      Return an iterator for the week day numbers that will be used for one
      week.  The first value from the iterator will be the same as the value of
      the :attr:`firstweekday` property.


   .. method:: itermonthdates(year, month)

      Return an iterator for the month *month* (1--12) in the year *year*. This
      iterator will return all days (as :class:`datetime.date` objects) for the
      month and all days before the start of the month or after the end of the
      month that are required to get a complete week.


   .. method:: itermonthdays(year, month)

      Return an iterator for the month *month* in the year *year* similar to
      :meth:`itermonthdates`, but not restricted by the :class:`datetime.date`
      range. Days returned will simply be day of the month numbers.  For the
      days outside of the specified month, the day number is ``0``.


   .. method:: itermonthdays2(year, month)

      Return an iterator for the month *month* in the year *year* similar to
      :meth:`itermonthdates`, but not restricted by the :class:`datetime.date`
      range. Days returned will be tuples consisting of a day of the month
      number and a week day number.


   .. method:: itermonthdays3(year, month)

      Return an iterator for the month *month* in the year *year* similar to
      :meth:`itermonthdates`, but not restricted by the :class:`datetime.date`
      range. Days returned will be tuples consisting of a year, a month and a day
      of the month numbers.

      .. versionadded:: 3.7


   .. method:: itermonthdays4(year, month)

      Return an iterator for the month *month* in the year *year* similar to
      :meth:`itermonthdates`, but not restricted by the :class:`datetime.date`
      range. Days returned will be tuples consisting of a year, a month, a day
      of the month, and a day of the week numbers.

      .. versionadded:: 3.7


   .. method:: monthdatescalendar(year, month)

      Return a list of the weeks in the month *month* of the *year* as full
      weeks.  Weeks are lists of seven :class:`datetime.date` objects.


   .. method:: monthdays2calendar(year, month)

      Return a list of the weeks in the month *month* of the *year* as full
      weeks.  Weeks are lists of seven tuples of day numbers and weekday
      numbers.


   .. method:: monthdayscalendar(year, month)

      Return a list of the weeks in the month *month* of the *year* as full
      weeks.  Weeks are lists of seven day numbers.


   .. method:: yeardatescalendar(year, width=3)

      Return the data for the specified year ready for formatting. The return
      value is a list of month rows. Each month row contains up to *width*
      months (defaulting to 3). Each month contains between 4 and 6 weeks and
      each week contains 1--7 days. Days are :class:`datetime.date` objects.


   .. method:: yeardays2calendar(year, width=3)

      Return the data for the specified year ready for formatting (similar to
      :meth:`yeardatescalendar`). Entries in the week lists are tuples of day
      numbers and weekday numbers. Day numbers outside this month are zero.


   .. method:: yeardayscalendar(year, width=3)

      Return the data for the specified year ready for formatting (similar to
      :meth:`yeardatescalendar`). Entries in the week lists are day numbers. Day
      numbers outside this month are zero.


.. class:: TextCalendar(firstweekday=0)

   This class can be used to generate plain text calendars.

   :class:`TextCalendar` instances have the following methods:

   .. method:: formatmonth(theyear, themonth, w=0, l=0)

      Return a month's calendar in a multi-line string. If *w* is provided, it
      specifies the width of the date columns, which are centered. If *l* is
      given, it specifies the number of lines that each week will use. Depends
      on the first weekday as specified in the constructor or set by the
      :meth:`setfirstweekday` method.


   .. method:: prmonth(theyear, themonth, w=0, l=0)

      Print a month's calendar as returned by :meth:`formatmonth`.


   .. method:: formatyear(theyear, w=2, l=1, c=6, m=3)

      Return a *m*-column calendar for an entire year as a multi-line string.
      Optional parameters *w*, *l*, and *c* are for date column width, lines per
      week, and number of spaces between month columns, respectively. Depends on
      the first weekday as specified in the constructor or set by the
      :meth:`setfirstweekday` method.  The earliest year for which a calendar
      can be generated is platform-dependent.


   .. method:: pryear(theyear, w=2, l=1, c=6, m=3)

      Print the calendar for an entire year as returned by :meth:`formatyear`.


.. class:: HTMLCalendar(firstweekday=0)

   This class can be used to generate HTML calendars.


   :class:`!HTMLCalendar` instances have the following methods:

   .. method:: formatmonth(theyear, themonth, withyear=True)

      Return a month's calendar as an HTML table. If *withyear* is true the year
      will be included in the header, otherwise just the month name will be
      used.


   .. method:: formatyear(theyear, width=3)

      Return a year's calendar as an HTML table. *width* (defaulting to 3)
      specifies the number of months per row.


   .. method:: formatyearpage(theyear, width=3, css='calendar.css', encoding=None)

      Return a year's calendar as a complete HTML page. *width* (defaulting to
      3) specifies the number of months per row. *css* is the name for the
      cascading style sheet to be used. :const:`None` can be passed if no style
      sheet should be used. *encoding* specifies the encoding to be used for the
      output (defaulting to the system default encoding).


   :class:`!HTMLCalendar` has the following attributes you can override to
   customize the CSS classes used by the calendar:

   .. attribute:: cssclasses

      A list of CSS classes used for each weekday. The default class list is::

         cssclasses = ["mon", "tue", "wed", "thu", "fri", "sat", "sun"]

      more styles can be added for each day::

         cssclasses = ["mon text-bold", "tue", "wed", "thu", "fri", "sat", "sun red"]

      Note that the length of this list must be seven items.


   .. attribute:: cssclass_noday

      The CSS class for a weekday occurring in the previous or coming month.

      .. versionadded:: 3.7


   .. attribute:: cssclasses_weekday_head

      A list of CSS classes used for weekday names in the header row.
      The default is the same as :attr:`cssclasses`.

      .. versionadded:: 3.7


   .. attribute:: cssclass_month_head

      The month's head CSS class (used by :meth:`formatmonthname`).
      The default value is ``"month"``.

      .. versionadded:: 3.7


   .. attribute:: cssclass_month

      The CSS class for the whole month's table (used by :meth:`formatmonth`).
      The default value is ``"month"``.

      .. versionadded:: 3.7


   .. attribute:: cssclass_year

      The CSS class for the whole year's table of tables (used by
      :meth:`formatyear`). The default value is ``"year"``.

      .. versionadded:: 3.7


   .. attribute:: cssclass_year_head

      The CSS class for the table head for the whole year (used by
      :meth:`formatyear`). The default value is ``"year"``.

      .. versionadded:: 3.7


   Note that although the naming for the above described class attributes is
   singular (e.g. ``cssclass_month`` ``cssclass_noday``), one can replace the
   single CSS class with a space separated list of CSS classes, for example::

         "text-bold text-red"

   Here is an example how :class:`!HTMLCalendar` can be customized::

       class CustomHTMLCal(calendar.HTMLCalendar):
           cssclasses = [style + " text-nowrap" for style in
                         calendar.HTMLCalendar.cssclasses]
           cssclass_month_head = "text-center month-head"
           cssclass_month = "text-center month"
           cssclass_year = "text-italic lead"


.. class:: LocaleTextCalendar(firstweekday=0, locale=None)

   This subclass of :class:`TextCalendar` can be passed a locale name in the
   constructor and will return month and weekday names in the specified locale.
   If this locale includes an encoding all strings containing month and weekday
   names will be returned as unicode.


.. class:: LocaleHTMLCalendar(firstweekday=0, locale=None)

   This subclass of :class:`HTMLCalendar` can be passed a locale name in the
   constructor and will return month and weekday names in the specified
   locale. If this locale includes an encoding all strings containing month and
   weekday names will be returned as unicode.

.. note::

   The :meth:`formatweekday` and :meth:`formatmonthname` methods of these two
   classes temporarily change the current locale to the given *locale*.  Because
   the current locale is a process-wide setting, they are not thread-safe.


For simple text calendars this module provides the following functions.

.. function:: setfirstweekday(weekday)

   Sets the weekday (``0`` is Monday, ``6`` is Sunday) to start each week. The
   values :const:`MONDAY`, :const:`TUESDAY`, :const:`WEDNESDAY`, :const:`THURSDAY`,
   :const:`FRIDAY`, :const:`SATURDAY`, and :const:`SUNDAY` are provided for
   convenience. For example, to set the first weekday to Sunday::

      import calendar
      calendar.setfirstweekday(calendar.SUNDAY)


.. function:: firstweekday()

   Returns the current setting for the weekday to start each week.


.. function:: isleap(year)

   Returns :const:`True` if *year* is a leap year, otherwise :const:`False`.


.. function:: leapdays(y1, y2)

   Returns the number of leap years in the range from *y1* to *y2* (exclusive),
   where *y1* and *y2* are years.

   This function works for ranges spanning a century change.


.. function:: weekday(year, month, day)

   Returns the day of the week (``0`` is Monday) for *year* (``1970``--...),
   *month* (``1``--``12``), *day* (``1``--``31``).


.. function:: weekheader(n)

   Return a header containing abbreviated weekday names. *n* specifies the width in
   characters for one weekday.


.. function:: monthrange(year, month)

   Returns weekday of first day of the month and number of days in month,  for the
   specified *year* and *month*.


.. function:: monthcalendar(year, month)

   Returns a matrix representing a month's calendar.  Each row represents a week;
   days outside of the month are represented by zeros. Each week begins with Monday
   unless set by :func:`setfirstweekday`.


.. function:: prmonth(theyear, themonth, w=0, l=0)

   Prints a month's calendar as returned by :func:`month`.


.. function:: month(theyear, themonth, w=0, l=0)

   Returns a month's calendar in a multi-line string using the :meth:`formatmonth`
   of the :class:`TextCalendar` class.


.. function:: prcal(year, w=0, l=0, c=6, m=3)

   Prints the calendar for an entire year as returned by  :func:`calendar`.


.. function:: calendar(year, w=2, l=1, c=6, m=3)

   Returns a 3-column calendar for an entire year as a multi-line string using
   the :meth:`formatyear` of the :class:`TextCalendar` class.


.. function:: timegm(tuple)

   An unrelated but handy function that takes a time tuple such as returned by
   the :func:`~time.gmtime` function in the :mod:`time` module, and returns the
   corresponding Unix timestamp value, assuming an epoch of 1970, and the POSIX
   encoding.  In fact, :func:`time.gmtime` and :func:`timegm` are each others'
   inverse.


The :mod:`calendar` module exports the following data attributes:

.. data:: day_name

   An array that represents the days of the week in the current locale.


.. data:: day_abbr

   An array that represents the abbreviated days of the week in the current locale.


.. data:: month_name

   An array that represents the months of the year in the current locale.  This
   follows normal convention of January being month number 1, so it has a length of
   13 and  ``month_name[0]`` is the empty string.


.. data:: month_abbr

   An array that represents the abbreviated months of the year in the current
   locale.  This follows normal convention of January being month number 1, so it
   has a length of 13 and  ``month_abbr[0]`` is the empty string.


.. seealso::

   Module :mod:`datetime`
      Object-oriented interface to dates and times with similar functionality to the
      :mod:`time` module.

   Module :mod:`time`
      Low-level time related functions.