DST (Daylight Saving Time) will be screwing up your Microsoft calendar. Isn't that great? MS has a Bulletin here. Changes take place on March 11, 2007. This is the best:
Consider any appointments and meetings in the extended DST period to be suspect. When in doubt, verify the correct time with the organizer.
Great, right? Why use an MS Calendar then? More info on calendars HERE.
"Please be assured that Google Calendar is compliant with this change." [Source]