Calculating time?

Hi there, I have to delete a database entry once 30 days (that is 2592000 seconds) have passed. I currently have my date in the following form: YearMonthDayHourMinuteSecond (everything has 2 digits so there are a total of 12 numbers). The code to produce the numbers looks like this: $cookvaldate = date("ymdHis"); Any recommendations on how I could calculate whether 30 days have passed? At this point in writing the code, I can still change the way how I store dates and time (so "yy-mm-dd hh:mm:ss" and everything else would be fine too). Could you please help me out? Code snippets would be highly appreciated Yours sincerely, Lauri Väin