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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