easter_days
(PHP 3>= 3.0.9, PHP 4 )
easter_days -- Get number of days after March 21 on which
Easter falls for a given year
Description
int easter_days ( [int year [, int method]])
Returns the number of days after March 21 on which Easter
falls for a given year. If no year is specified, the current
year is assumed.
Since PHP 4.3.0, the year parameter is optional and defaults
to the current year according to the localtime if omitted.
The method parameter was also introduced in PHP 4.3.0 and
allows to calculate easter dates based on the Gregorian
calendar during the years 1582 - 1752 when set to CAL_EASTER_ROMAN.
See the calendar constants for more valid constants.
This function can be used instead of easter_date() to calculate
Easter for years which fall outside the range of Unix timestamps
(i.e. before 1970 or after 2037). Example 1. easter_days()
example
<?php
echo easter_days(1999); // 14, i.e. April 4
echo easter_days(1492); // 32, i.e. April 22
echo easter_days(1913); // 2, i.e. March 23
?>
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 also easter_date().
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