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>easter_date</A
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>easter_date -- get UNIX timestamp for midnight on Easter of a given year</DIV
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><H2
>Description</H2
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><CODE
CLASS="FUNCDEF"
>int easter_date</CODE
>(int year);<P
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><P
> Returns the UNIX timestamp corresponding to midnight on
Easter of the given year. If no year is specified, the
current year is assumed.
</P
><P
> <I
CLASS="emphasis"
>Warning:</I
> This function will generate
a warning if the year is outside of the range for UNIX
timestamps (i.e. before 1970 or after 2037).
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>Example 1. <B
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>easter_date()</B
> example</B
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> 1
2 echo date( "M-d-Y", easter_date(1999) ); /* "Apr-04-1999" */
3 echo date( "M-d-Y", easter_date(2000) ); /* "Apr-23-2000" */
4 echo date( "M-d-Y", easter_date(2001) ); /* "Apr-15-2001" */
5 </PRE
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><P
> 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.
</P
><P
> (The code is based on a C program by Simon Kershaw,
<webmaster@ely.anglican.org>)
</P
><P
> See <A
HREF="function.easter-days.html"
><B
CLASS="function"
>easter_days()</B
></A
> for calculating Easter
before 1970 or after 2037.
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