# 5.19 `calendar` -- General calendar-related functions

This module allows you to output calendars like the Unix 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 `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.

Most of these functions rely on the `datetime` module which uses an idealized calendar, the current Gregorian calendar indefinitely extended 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.

`setfirstweekday`( | weekday)

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

      import calendar
      calendar.setfirstweekday(calendar.SUNDAY)

  New in version 2.0.

`firstweekday`( | )

  Returns the current setting for the weekday to start each week. New in version 2.0.

`isleap`( | year)

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

`leapdays`( | y1, y2)

  Returns the number of leap years in the range [y1...y2), where y1 and y2 are years. Changed in version 2.0: This function didn't work for ranges spanning a century change in Python 1.5.2.

`weekday`( | year, month, day)

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

`weekheader`( | n)

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

`monthrange`( | year, month)

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

`monthcalendar`( | year, month)

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

`prmonth`( | theyear, themonth[, w[, l]])

  Prints a month's calendar as returned by `month()`.

`month`( | theyear, themonth[, w[, l]])

  Returns 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 set by `setfirstweekday()`. New in version 2.0.

`prcal`( | year[, w[, l[c]]])

  Prints the calendar for an entire year as returned by `calendar()`.

`calendar`( | year[, w[, l[c]]])

  Returns a 3-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 set by `setfirstweekday()`. The earliest year for which a calendar can be generated is platform-dependent. New in version 2.0.

`timegm`( | tuple)

  An unrelated but handy function that takes a time tuple such as returned by the `gmtime()` function in the `time` module, and returns the corresponding Unix timestamp value, assuming an epoch of 1970, and the POSIX encoding. In fact, `time.gmtime()` and `timegm()` are each others' inverse. New in version 2.0.

See Also:

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

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