Jens Olsen's World Clock

A Mechanical Wonder Born from Inspiration

Jens Olsen's World Clock stands as one of the most remarkable achievements in horological history. The story begins in 1897 when a young locksmith named Jens Olsen, then just 25 years old, visited Strasbourg and encountered the astronomical clock at Notre-Dame Cathedral. This encounter sparked a lifelong obsession. Olsen dedicated himself to mastering watchmaking and spent years calculating and planning his own comprehensive astronomical clock—a project that would consume the remainder of his life and outlive him by a decade.

Engineering Precision Across 15,448 Parts

The clock's complexity is staggering. It comprises 12 independent movements working in concert, with a total of 15,448 precisely calibrated parts. The fastest gear completes a revolution every ten seconds, while the slowest turns at a glacial pace—one complete rotation every 25,753 years. This extraordinary range of speeds allows the clock to simultaneously track immediate time and cosmic cycles spanning millennia. The construction materials reflect meticulous attention to detail: the gearing and module structure are largely gold-plated brass, while the dials are rhodium plated. The pendulum rod is made of Invar, and the impulse rods are sapphire, ensuring durability and accuracy across centuries.

From Vision to Reality: A Collaborative Achievement

Olsen began the actual production phase in 1943, assembling a skilled team of craftspeople to bring his calculations to life. However, illness claimed him in 1945, before the clock's completion. The project was carried forward by Otto Mortensen, a young clockmaker, working alongside architect Gunnar Biilmann Petersen, who designed the clock's striking exterior. After more than a decade of careful calibration and assembly, the masterpiece was finally set in motion at precisely 3 p.m. on December 15, 1955, by King Frederik IX and Olsen's youngest grandchild, Birgit—a symbolic moment honoring both the creator's legacy and the collaborative effort that brought his vision to completion.

A Display of Astronomical and Temporal Knowledge

The clock's dials reveal an extraordinary range of information. Beyond displaying local time and true solar time, it shows the exact time at locations around the globe through its Synchronoscope—a dial featuring a fixed map around which a 24-hour dial rotates. The clock calculates sunrises and sunsets, tracks the positions of stars and planets with remarkable precision, displays lunar and solar eclipses, and maintains a perpetual Gregorian calendar that automatically accounts for leap years and changing holiday dates far into the future. This comprehensive astronomical display transforms the clock into both a timekeeping device and an educational instrument about our place in the cosmos.

Preservation and Modern Display

The clock is housed in a dedicated room within City Hall, enclosed in a large glass case with wooden and stainless steel framing, sitting on a granite base. The enclosure features internal lighting and is maintained at precise temperature and humidity levels by a ventilation system in the building's basement. This careful environmental control ensures the mechanism's longevity. A restoration process undertaken between 1995 and 1997 by Danish clock conservation specialist Søren Andersen returned the clock to optimal working condition. Today, visitors can view the clock from all sides, appreciating both its intricate mechanical beauty and the profound knowledge embedded within its design.

A Legacy of Human Ingenuity

Jens Olsen's World Clock represents far more than a functional timepiece. It embodies decades of astronomical calculation, mechanical innovation, and artistic craftsmanship. The clock stands as a testament to human curiosity about time, space, and our relationship to the cosmos. Its requirement for winding just once per week, combined with its projected accuracy for 2,500 years, speaks to the timeless quality of precision engineering. For visitors, the clock offers a window into both the history of horology and the enduring power of a single person's vision to create something that will outlast generations.