OK so I have a lot of appointments in an outlook calendar (about 12 each day). It was synced to my Galaxy 3G. I wanted to delete all of them for one day, so deleted multiple appointments but I didn't get the option to specify whether I wanted to delete a single event or a recurring event - and as a default it deleted all recurring events (hence all of my future appointments .. lots!). I decided to sync with my outlook calendar thinking that it would replace all of the deleted appointments, however it synced in the other direction and has wiped them all from my outlook calender as well as my phone calender. Really could do with some advice how to 'undo' the delete on the phone or where else I may find the original data to recover it (I have looked at the outlook calendar and the data is not in the trash as it would be if I had deleted the data via outlook itself).
This question is related more to Outlook than Android. Android syncs with google calendar and even if that case, deleted calendar events cannot be recovered (Google Support - Can I recover a deleted Calendar event? You can try to:
Other than that I can't think of any other way of restoring your calendar events