In case you missed it, earlier this month the publishers of php|architect magazine published a definitive guide to working with dates and times in PHP (by Derick Rethans). Marco Tabini posted about it to his blog:

Date and time programming is one of those topics that almost everybody tends to think they're doing well and almost nobody does correctly. Thus, the most challenging aspect of selling this book is the fact that almost all those who could benefit from it - and that's just about everybody - will tend to think that they don't need it.

Marco mentions a specific time when the updates to the date/time handling in PHP caused issue for them (like changes to the need to set a default timezone) and how having the information in Derick's book would have helped immediately.

You can find out more information about the book (and order your own copy) on this page of the php|architect site.