Restore Deleted Events In Google Calendar
If for any reason your Google Calendar events go missing and you need to restore them, Google allows you to restore up to the last 30 days of deleted calendar items.
1. Sign into your Google account in a Web browser (Internet Explorer, Chrome, FireFox, etc)
2. On the left will be a list of "My Calendars"
3. To the right of your actual calendar name (not "My Calendars"), click the drop down menu Down arrow and go select View Trash.
4. Check the box to the left of any events you want to restore or click the box at the top left to select all events.
5. Click Restore selected events.