Can I restore individual iCal appointments using Time Machine?
I asked staff at the Apple Store the same question, who consulted with a Genius. As of Mountain Lion, it is still not possible to go into Time Machine via iCal/Calendar. In other words, the only solution is to manually restore deleted entries from raw iCal/Calendar files (located in ~/Library) using Time Machine.

There is a related discussion on Apple Support Communities:


https://discussions.apple.com/thread/3851319?start=0&amp;tstart=0


The person I spoke to also reminded me to turn off iCloud before attempting the restore procedure, as it may corrupt existing calendars.