Jens Olsen's World Clock, which resides at City Hall in Copenhagen, is a very advanced astronomical clock finished in 1955.

Jens Olsen's World Clock houses 12 separate clockworks and consists of 15.448 separate parts. The central piece is a weighted clock, that measures perfectly. The World Clock shows Siderean and Central European time, and it controls 10 additional clockworks.

Jens Olsen's World Clock was constructed based on careful measurements taken during many years.

The mechanical World Clock must be wound up once a week.