easter_date

(PHP 4, PHP 5, PHP 7)

easter_date — Get Unix timestamp for midnight on Easter of a given year

Description

easter_date ([ int|null $year = null [, int $mode = CAL_EASTER_DEFAULT ]] ) : int

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

Warning

This function will generate a warning if the year is outside of the range for Unix timestamps (i.e. typically before 1970 or after 2037 on 32bit systems).

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.

Parameters

year: The year as a number between 1970 an 2037. If omitted or null, defaults to the current year according to the local time.
mode: Allows Easter dates to be calculated based on the Julian calendar when set to CAL_EASTER_ALWAYS_JULIAN. See also calendar constants.

Return Values

The easter date as a unix timestamp.

Changelog

Version	Description
8.0.0	`year` is nullable now.

Examples

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

?>

Notes

Note:

easter_date() relies on your system's C library time functions, rather than using PHP's internal date and time functions. As a consequence, easter_date() uses the TZ environment variable to determine the time zone it should operate in, rather than using PHP's default time zone, which may result in unexpected behaviour when using this function in conjunction with other date functions in PHP.

As a workaround, you can use the easter_days() with DateTime and DateInterval to calculate the start of Easter in your PHP time zone as follows:
<?php
function get_easter_datetime($year) {
    $base = new DateTime("$year-03-21");
    $days = easter_days($year);

    return $base->add(new DateInterval("P{$days}D"));
}

foreach (range(2012, 2015) as $year) {
    printf("Easter in %d is on %s\n",
           $year,
           get_easter_datetime($year)->format('F j'));
}
?>
The above example will output:
Easter in 2012 is on April 8
Easter in 2013 is on March 31
Easter in 2014 is on April 20
Easter in 2015 is on April 5