Jens Olsen's World Clock at Copenhagen City Hall

Jens Olsen, a locksmith and clockmaker in Copenhagen, created this master piece of an advanced astronomical clock from 1943 with planning from 1934-1936. He died 1945, 10 years before it was completed by his closest employee Otto Mortensen.

It's the most precise mechanical clock in the World, only atomic clocks are more precise.

1995 a tourist noticed that the clocks astronomical part was not showing the right positions. That was a result of the pollution in the air of Copenhagen. It took two years to clean it.

It has 12 works with 14,448 parts, the gears are gold plated. The slowest gear turn one round in 25.753 years, the fastest in 10 seconds.

The clock shows the following:
Middle Eastern European Time.

Middle solstice, True sunshine and startime for Copenhagen as well as the time equation and the combination of time equation and locale constant.

Middle Ages for various geographical longitude.

The stars' meridian passages as well as the ups and downs.

Accuracy and their impact on the rise and fall of the stars.

Sun's meridian passages as well as ups and downs.

The phases of the moon.

The geocentric lengths of the sun and the moon.

Moon lane rental and and in conjunction with it, times for future solar and moon eclipses.

The length of the moon lane.

The great planets distance to the sun.

A fully automatic Gregorian calendar, each New Year's Eve at 00:00, calculates all the chronological elements of this calendar, as well as concepts such as solar circle, dictionaries, gold numbers, epitems and search letters, then weekdays and floating holidays in the coming year (Easter, Pentecost, etc.) are marked in the calendar .

Year, day of week, date, month and day of the 7980-year-old Julian period.