Check if a time in a timezone is elapsed in php?

H开发者_如何学JAVAere's the time entered by a user CDT 2011-02-01 16:30:00

How do i know that if that time was passed already in php?

Thanks

$usertime = strtotime('CDT 2011-02-01 16:30:00');
if (time() > $usertime) echo 'time passed';