This article describes the limitations of Bookings Calendar when it comes to changing owners.

Virginia Tech admins lack all administrative control over Bookings Calendar. Microsoft recommends that the original owner make the transfer themselves or that someone log in as the owner to do it (in the case of orphaned objects). We cannot do that at Virginia Tech for reasons that range from security to privacy.

Normally, the way to prevent this is to tie a Bookings Calendar to a departmental shared resource, but again, this is not possible. Microsoft requires that the calendar be tied to an individual account, because the license is tied to an individual.

In the case of the calendar being owned by a former employee or student at the university, the calendar will be deleted when their account is deleted: Employee (45 or so days); Student (2 major semesters and 60 days). This is a long time to wait. Therefore, moving forward it is best to ensure that offboarding is done before the person is no longer affiliated with the university.