$ctime
From Scriptwiki
Returns total number of seconds elapsed since 00:00:00 GMT, January 1, 1970 based on your system time or on the time you have specified.
$ctime $ctime(text)
$ctime without properties is equivalent to $ctime(January 1 1970 00:00:00).
Example
$ctime(24/12/2004 12:00)
This will return 1103886000, as it is total number of seconds from January 1, 1970, 00:00 until December 24, 2004, 12:00.
if ($ctime > $ctime(25th December 2005)) { echo -ag Its past christmas 2005 :< }
This will check to see if it's after the 25th of December 2005
See Also
$asctime returns the time and date in text format associated with the $ctime time value.