"Have you ever accidentally deleted an event, or several, from your calendar? Lost meetings, conference calls, customer reservations and appointments… you know how devastating that can be. Not just to your day, but to your business.
Google says, “Once an event is deleted, its full details can’t be recovered.” Spanning says, “We beg to differ!”
With Spanning’s Undelete for Google Calendar, your deleted events can be undeleted, with details intact. Here’s the thing to know… once an event is deleted, that data sticks around for a while before it’s permanently gone – it’s just a matter of finding and recovering it..." - This requires a Google Apps account.