On his blog today, Joakim Nygard has posted about the use (or disuse) of time zones in PHP:
The problem with not handling timezones correctly is not apparent in the usual case of the webserver and the database server being in the same timezone. [...] Often a specific timezone is assumed for displaying date and time. This could very well be incorrect for a large number of visitors. If the database server is in yet another timezone, things begin to get out of sync.
He mentions the time zone functionality that MySQL offers too, but notes that it cannot be relied on either. Thankfully, there's is a bit of hope in PHP5 (as of 5.1 in fact) - the date_default_timezine_set function. He includes an example of the function in use, making it simple to get the correct date and time automatically with the date() function without having to do any hacks to discover the correct time zone.