Transfer ownership of a calendar
It's not possible to merge two Google Calendars at this time, but you can share a calendar with a new owner. Be sure to select "Make changes and manage sharing" in the permission level drop-down menu to effectively extend administrative abilities to the new owner.
Note: While the new owner will have access to edit and make changes to the calendar, if the previous owner is deleted the calendar will also be deleted. If you wish to delete the previous owner, we recommend exporting the calendar's events and importing them into the new calendar first to prevent losing the calendar.