Sometimes you may want to clear or Reassign 'owned' contacts - such as when an employee goes on vacation.
NOTE: This only clears or reassigns the Contact Ownership, not the actual reminder or Calendar entry.
Edit the User Account (assuming the user was not deleted)
Click the Admin Tab, scroll to the bottom
Reset the Owned Contacts, or Reassign to another user
This can also be done from a Campaign:
On the Admin Tab, choose Purge Contact Owners. This will purge ALL assigned Contact Owners that are inactive or older than 30 days.