Find Out the Owner
The first thing we'll need to do is find out the owner of a shared calendar if you're looking to transfer ownership. For those of you who already know this just skip ahead, but it's important to know this going forward.
Simply click the little down arrow on the shared calendar in question, then select "Calendar Settings". Here you can find the owner of the calendar. If the owner’s name is not displayed, you may have to do some investigating within your company to find the owner.
Once you find out the owner, you will need to contact the user and request they transfer ownership of the calendar.
Transfer Ownership
The owner of the calendar can share the calendar with a specific person to transfer ownership. First, that person needs to go to "Calendar Settings".
Then select the "Calendars" tab and select the calendar you wish to share. Next, click on the "Share this Calendar" tab. Here you can enter the email address of the user you would like to share the calendar with and change the ‘Permission Settings’ to ‘Make changes AND manage sharing’.
Finally, don't forget to click "Save"! Now if the previous user leaves your organization, the calendar will still be perserved.
Have you ever had to transfer ownership of a calendar in Google Apps?