Once again this is the year for the perpetual calendar to shine. Leap year is when we distinguish the good from the not so good in watches. In two ways actually. Not only do we need the watches to show us the extra day in February, we also demand that they switch to March 1st on the correct day.

It may sound simple, but in real life this is af ormidable technical and mechanical challenge. A four-year interval need a program that differentiate a 48 month cycle. As a rule, this task is handled by a wheel with 48 teeth in which the durations each month during a four-year period are permanently stored in the form of gaps that have different depths.Perpetual calendar leap year

Perpetual calendar leap year


With the Lange 1 Tourbillon Perpetual CalendarA. Lange & Söhne chose a totally different approach on the new L082.1 movement. They placed the month indication on a large circumferential ring that rotates about its centre axis once a year in twelve 30-degree steps. The month ring is driven via its internal gearing. It rotates about its own axis once a year. The inside of the gear rim features a circumferential contour with wavy recesses. A spring-loaded sampler lever glides along this contour and is deflected by a magnitude that corresponds to the depth of the respective recess. The more it is deflected, the shorter the month. The leap year indicator is in contact with the sampler lever and in February every fourth year the display is extended by one day.
Perpetual calendar leap year
Perpetual calendar leap year


All displays of the perpetual calendar switch forward instantaneously, so they deliver precise readings at all times. The force needed for the switching cycles is gradually built up during a period of 24 hours. For this reason, the switching process does not affect rate accuracy. This requires two mechanical energy storage devices – one for advancing the date, the day-of-the week, and the moon-phase display on a daily basis, and the second one to switch the month ring and the leap-year disc.

The mechanism is designed such that a first one-day correction is not needed until the year 2100. In 2100, the centennial rule of the Gregorian calendar omits the leap year and skips 29 February as an exception.

Read more about the watches at A. Lange & Söhne.

Perpetual calendar leap year


The fascination for workmanship, quality and design led Kristian to start Gyrus. After years of trawling specialist websites and forums he felt a need for his passions to be collected on one site. Watches, classic cars, gourmet food and whisky is his specialities.

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