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

?>


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



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 07:50


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



// 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:



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 10:46


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



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
09-Nov-2004 12:17


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; 



   } 

?>

ray at non-aol dot com
07-Nov-2004 08:49


The algorithm from BigTree will throw an error in 2021 and 2025.  Better to install the PHP functions!  Details here:



http://aa.usno.navy.mil/faq/docs/easter.html

bigtree at 29a dot DONTSPAM dot nl
17-May-2002 11:41


A much smaller hack is the following. I ported this from a Delphi implementation of a function calculating easter dates.





<?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 - ($C / 4) - ((8*$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, 22 Aug 2008