easter_date

(PHP 4, PHP 5)

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.

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>)

Parameters

year: The year as a number between 1970 an 2037

Return Values

The easter date as a unix timestamp.

Changelog

Version	Description
Since 4.3.0	The `year` parameter is optional and defaults to the current year according to the local time if omitted.

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

?>


In 5.3.1 easter_date() returns GMT of start of Easter Day in UK allowing

for UK Summer Time. If you are in another time zone you need to 

calculate offsets.

<?php

        $e1 = easter_date(2008);

        $e2 = easter_date(2009);

        echo "Timestamps " . $e1 . " " . $e2 . "\n";



        //      Timestamps 1206230400 1239490800



        echo "Days between Easter 2008 Easter 2009 = " . ($e2-$e1)/86400 . "\n";



        //      Days between Easter 2008 Easter 2009 = 384.958333333 - i.e. 384 days 23 hours



        date_default_timezone_set("Europe/London");

        echo date( " l, jS F Y H:i TO",$e1) . "\n";

        echo date( " l, jS F Y H:i TO",$e2) . "\n";



        //      Sunday, 23rd March 2008 00:00 GMT+0000

        //      Sunday, 12th April 2009 00:00 BST+0100



        date_default_timezone_set("America/New_York");

        echo date( " l, jS F Y H:i TO",$e1) . "\n";

        echo date( " l, jS F Y H:i TO",$e2) . "\n";



        //      Saturday, 22nd March 2008 20:00 EDT-0400

        //      Saturday, 11th April 2009 19:00 EDT-0400

        //      Daylight saving time in effect - New York 4 hours behind GMT

?>

maxie
12-Jun-2008 08:36


To compute the correct Easter date for Eastern Orthodox Churches I made a function based on the Meeus Julian algorithm:





<?php


function orthodox_eastern($year) {


    $a = $year % 4;


    $b = $year % 7;


    $c = $year % 19;


    $d = (19 * $c + 15) % 30;


    $e = (2 * $a + 4 * $b - $d + 34) % 7;


    $month = floor(($d + $e + 114) / 31);


    $day = (($d + $e + 114) % 31) + 1;


    


    $de = mktime(0, 0, 0, $month, $day + 13, $year);


    


    return $de;


}


?>

nigelf at esp dot co dot uk
28-Jan-2008 11:50


v5.2.1 - There is a known bug with easter_date() that can return incorrect dates for some years:





<?php


// 2008 OK


echo date("D d M Y", easter_date(2008));  // Sun 23 Mar 2008





// 2009 returns Saturday


echo date("D d M Y", easter_date(2009));  // Sat 11 Apr 2009


?>








However easter_days() works correctly:





<?php


echo date("D d M Y", strtotime("2009-03-21 +".easter_days(2009)." days"));  // Sun 12 Apr 2009


?>





It is apparently related to timezone settings.

14-Aug-2006 02:46


I made the function like this ... works fine !





<?php


function ostern


{


    $maerz21=date('z',mktime(0,0,0,3,21,$jb));





    $d=((15 + $jb/100 - $jb/400 - (8 * $jb/100 + 13) / 25)%30 + 19 * ($jb%19))%30;





    if ($d==29)


    {


        $D=28;


    }


    elseif($d==28 && ($jb%17)>=11)


    {


        $D=27;


    }


    else $D=$d;    





    $e=(2 * ($jb%4) + 4 *($jb%7) + 6 * $D + (6 + $jb/100 - $jb/400 - 2)%7)%7;





    $ostersonntag=$e+$D+1+$maerz21;


    return $ostersonntag;


}


?>

phpuser
08-Nov-2004 04:17


The algorithm from Bigtree is correct if you add some (int) cast

<?php 

   function easter_date ($Year) { 

   

       /* 

       G is the Golden Number-1 

       H is 23-Epact (modulo 30) 

       I is the number of days from 21 March to the Paschal full moon 

       J is the weekday for the Paschal full moon (0=Sunday, 

         1=Monday, etc.) 

       L is the number of days from 21 March to the Sunday on or before 

         the Paschal full moon (a number between -6 and 28) 

       */ 

       



         $G = $Year % 19; 

         $C = (int)($Year / 100); 

         $H = (int)($C - (int)($C / 4) - (int)((8*$C+13) / 25) + 19*$G + 15) % 30; 

         $I = (int)$H - (int)($H / 28)*(1 - (int)($H / 28)*(int)(29 / ($H + 1))*((int)(21 - $G) / 11)); 

         $J = ($Year + (int)($Year/4) + $I + 2 - $C + (int)($C/4)) % 7; 

         $L = $I - $J; 

         $m = 3 + (int)(($L + 40) / 44); 

         $d = $L + 28 - 31 * ((int)($m / 4)); 

         $y = $Year; 

         $E = mktime(0,0,0, $m, $d, $y); 



         return $E; 



   } 

?>

add a note

easter_days

cal_to_jd

Last updated: Fri, 05 Feb 2010