[Closed] Syncing calendars....ahhhhhhhhhhhhhhh

Here's a headache if ever there was one.

All my 'all day' diary events (in Outlook) have suddenly changed to span two days. A quick check and the time has shifted back an hour, so what was recorded on entry as 00.00 - 00.00 is now 23.00 to 23.00, so for example every birthday is now showing as starting a day early and spanning two days.

I recently added Google Calendar sync but set this as one way (to Google), so it should have had no impact. I'm guessing that a device or service I'm syncing is set to a different time zone and has pulled everything back an hour, but that's a guess.

Anyone seen this and no how to hunt it down and kill it. I want blood! Very annoying.

EDIT: just checked and it is not global. Some entries have remained correct.