On the SitePoint PHP blog today they pose a question to all PHP developers out there - is your application affected by the Y2K38 bug?

I don't want to be too alarmist, but try running the [given] PHP code on your system. [...] With luck, you'll see "Wednesday 1 February 2040 00:00" displayed in your browser. If you're seeing a date in the late 60's or early 70's, your PHP application may be at risk from the Y2K38 bug!

The bug, caused by a 32-bit operating system, can be helped by running the application on a 64-bit platform (it's due to the limitation of integer size), but there is another option - the DateTime class that handles dates and times differently than the just using the local time settings.