The Calendar Edit History provides a history of all edits made to a Calendar by you or any Visitor to your Calendar with Edit Rights to the calendar. With the edit history, you can protect calendar data with real-time backups and recover a deleted calendar entry. If you delete any events in your calendar the deletions will be recorded in the Calendar Edit History.

While you can use the Calendar Backups to restore your entire calendar to a previous version, you also have the option of restoring a single event to your calendar. If you have deleted an Event you can restore it to your calendar using the Calendar Edit History. All you need to do is go to the Calendar Edit HIstory, search for your deleted event, and then click on the "Restore" button next to it. Follow the steps in the image below:

Once you're in the Calendar Edit History make sure that you have the "Deleted" option selected for the "Only show these edit actions" option. This will make it easier to review only the events that have been deleted from your calendar. You can then click on the "Restore" button next to the event you want to restore to your calendar. See the image below: