Verifying the date

How can i check if a date is bigger than other date ?
there is a function i can use to do this job?

What format is it?

DD/MM/YY

i was doing this:

if( ( $today < $end_date ) or ( $end_date =="" ) or ( $end_date ==NULL ) ) {
//go to one website
} else {
//display a "not allowed" message
}

but did not work because the way i am doing 1999 is greater than 2004 as i am using YY (so 99 >04)

How can i fix it ?

try that:

suppose you've got
$date1, $date2.

if( strtotime($date1) > strtotime($date2) )
       // date1 is bigger.
else
      // date 2 is bigger.

It works ! thank´s my doubt is that if strtotime works with dd/mm/yy format or it does not make a diference?

If yes how do strtotime works with this format?