On PHPMaster.com today there's a new tutorial by Sean Hudgston about working with dates and times via the PHP date functions and how they cooperate with dates/times from a MySQL database.

When working in any programming language, dealing with dates and time is often a trivial and simple task. That is, until time zones have to be supported. Fortunately, PHP has one of the most potent set of date/time tools that help you deal with all sorts of time-related issues: Unix timestamps, formatting dates for human consumption, displaying times with time zones, the difference between now and the second Tuesday of next month, etc. In this article I'll introduce you to the basics of PHP's time functions (time(), mktime(), and date()) and their object-oriented counterparts, and then take a look at MySQL dates and show you how to make them play nicely with PHP.

His examples include how to get the current Unix time, formatting dates/times, making timestamps and working with the more powerful DateTime objects. On the MySQL front, he shows the result of a normal date select, one using the "unix_timestamp" function and how to shift the result based on the user's timezone.