After OSX 10.6.3 was released the sync services between iCal and Entourage went a little screwy. Many calendar entries were flagged as conflicts (usually items with invites) but the sync service wouldn’t allow them to be merged. Since I have several Macs connected into my Exchange account, multiple entries started to appear. The solution was to switch off Entourage’s iCal sync, delete the Entourage calendar from iCal and then re-enable syncing so that a new calendar is created.
Although I had fixed my work Mac and my main Mac at home, on my old laptop, I’d been ignoring the conflicts. However, the warning message were starting to get annoying so I decided to re-sync the calendars. However, I forgot to switch of the Exchange/iCal sync option before deleting the calendar from iCal and before I knew it, Entourage synced all deletions to Exchange.
I’ve found an easy way to restore all deleted calendars. My solution requires a second Mac but I suspect that the solution will work if you’re restoring the calendar from a local backup. First switch off your network connection and then open Entourage. Backup your Exchange calendar to your ‘local calendar’. The easiest way is to use the ‘All Events’ option to select all calendar entries and move them into your ‘Local Calendar’. You can then reconnect to your network and sync with Exchange. Once the sync is complete, copy back all entries into your Exchange calendar and re-sync.