   #PHP Manual Calendar functions cal_to_jd easter_days

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                                  easter_date

   (PHP 3>= 3.0.9, PHP 4 )
   easter_date --  Get Unix timestamp for midnight on Easter of a given
   year

Description

   int easter_date ( [int year])

   Returns the Unix timestamp corresponding to midnight on Easter of the
   given year.

   Since PHP 4.3.0, the year parameter is optional and defaults to the
   current year according to the localtime if omitted.

   Example 1. easter_date() example
   <?php
   echo date("M-d-Y", easter_date(1999));        // Apr-04-1999
   echo date("M-d-Y", easter_date(2000));        // Apr-23-2000
   echo date("M-d-Y", easter_date(2001));        // Apr-15-2001
   ?>

   Warning

   This function will generate a warning if the year is outside of the
   range for Unix timestamps (i.e. before 1970 or after 2037).

   The date of Easter Day was defined by the Council of Nicaea in AD325
   as the Sunday after the first full moon which falls on or after the
   Spring Equinox. The Equinox is assumed to always fall on 21st March,
   so the calculation reduces to determining the date of the full moon
   and the date of the following Sunday. The algorithm used here was
   introduced around the year 532 by Dionysius Exiguus. Under the Julian
   Calendar (for years before 1753) a simple 19-year cycle is used to
   track the phases of the Moon. Under the Gregorian Calendar (for years
   after 1753 - devised by Clavius and Lilius, and introduced by Pope
   Gregory XIII in October 1582, and into Britain and its then colonies
   in September 1752) two correction factors are added to make the cycle
   more accurate.

   (The code is based on a C program by Simon Kershaw, <webmaster at
   ely.anglican dot org>)

   See easter_days() for calculating Easter before 1970 or after 2037.
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