As ran-o-matic said - you're probably missing the daylight savings time patch on either your desktop or pda. If you do a windows update on your desktop you'll get it.
If you need the one for your pda, get it here:
http://ota.wsync.com/WSWM5PPC.cab
..and here is a good article explaining it all:
http://news.com.com/2100-1041_3-6159908.html