A synchronous world clock which allows a user to determine the exact time at any location on earth is disclosed. The clock is comprised of a planisphere of the earth, a time scale surrounding the planisphere and a drive for rotating the planisphere counterclockwise relative to the time scale once every...http://www.google.com/patents/US4579460?utm_source=gb-gplus-sharePatent US4579460 - Synchronous world clock
