Derick Rethans 
@derickrDerick Rethans is a PHP internals expert, author of Xdebug and an OpenStreetMap and mapping enthusiast. He has contributed in a number of ways to the PHP project, including the Xdebug debugging tool, and various extensions and additions. He’s a frequent lecturer at conferences, the author of php|architect’s Guide to Date and Time Programming, and the co-author of PHP 5 Power Programming. He’s now working with 10gen to help improve the MongoDB PHP driver.
Practical Date/Time Handling with PHP 
Dates, times and timezones are a complicated matter to deal with. Luckily, PHP has powerful date/time handling functionality. It allows you to deal with many issues that arise when you are developing applications. This talk will cover advanced functionality of PHP’s date/time functionality and is not an introduction except for where this is necessary. I will cover dealing with timezones, calculations with DateTime objects and tips and tricks for dealing with storing date/time information in a database.
http://blip.tv/play/h75rg4qkMAA?p=1
Slides available here as a PDF download.
