The Energy Policy Act of 2005 states that daylight saving time is extended by four weeks beginning in 2007. This means you need to update your Windows Mobile device to reflect this change. While Microsoft is working on an "official" release for the update, we published an article with the required registry changes that has now been turned into a easy-to-install CAB file. Of course, you should use it at your own risk - or wait for the Microsoft release.

 

You can read more and get the link to the download on Vik's blog 

http://blogs.technet.com/vik/archive/2007/01/20/2007-daylight-savings-issues-for-windows-mobile-2003-and-5-0.aspx