esnupe,
between change of daylight saving and update of itunes I had at least one sync and didn't recognize any calendar entry wrong. I would have recognized because my first wrong entry now is "Good Friday" which is on the iphone shown now yesterday.
My guess is that the new itunes version has difficulties with identifying timezones and DST and depending on which entries it finds first, gets on a wrong track. looking to other threads, I found quite a number of people who have appointments shifted by 1 hour, which is not the case for me. But I have currently only a few appointments in the future and they are after the all-day-events. If those are shifted also just by theoretically one hour, it means one day, because of the all-day.
In case your are interested in more details from my side, see this one
http://discussions.apple.com/message.jspa?messageID=11307225#11307225
Até breve