Date and Time
most used
strtotime
description
The function expects to be given a string containing a US English date format and will try to parse that format into a Unix timestamp (the number of seconds since January 1 1970 00:00:00 GMT), relative to the timestamp given in $now, or the current time if $now is not supplied.
declaration of strtotime
int strtotime ( string $time [, int $now ] )