Challenging the Leap Year: A. Lange & Söhne

Once every four years, we get an extra day, and 2020 is one of those -a leap years. While most of us use calendars, apps and other methods to track our days, purists like to use their watches. And more specifically, watches with one complication, the perpetual calendar. Since 2001, A. Lange & Söhne has launched eight timepieces with that feature. But rather than sticking to how things were done in the past, the Saxon manufacture has decided to do things differently.

LANGE 1 TOURBILLON PERPETUAL CALENDAR full mechanism
LANGE 1 TOURBILLON PERPETUAL CALENDAR (calibre L082.1)
The Classical Way

The leap year is what separates perpetual calendars from their annual counterpart. It all starts on New Year’s Eve when, at midnight, the leap year indication switches from 3 to 4. From then, it takes 59 days until the perpetual calendar can finally demonstrate what it is capable of. It will correctly reproduce the transition from 28 to 29 February, but subsequently also switches directly to 1 March at midnight of the leap day.

In theory, it sounds quite simple. But it is a technical prowess requiring the development of a mechanical program that maps different durations of months across an entire four-year cycle. This task is classically handled by a programme wheel with 48 notches and steps. These correspond to the different durations of the 48 months in the four-year cycle of three regular years and a leap year.

Mechanism showing the assembly of the leap-year indication, with numeral disc positioned on top of the leap-year arbour
LANGE 1 TOURBILLON PERPETUAL CALENDAR (calibre L082.1)
The Lange Way

The perpetual calendar is a complication that achieves wonders but is quite restraining when it comes to design. Many watchmakers have tried to incorporate additional complications but never really succeeded.

The perpetual calendar is a complication that achieves wonders but is quite restraining when it comes to design. Many watchmakers have tried to incorporate additional complications but never really succeeded.

Undeterred by this, the calibre designers at A. Lange & Söhne set out on a new path in the design of perpetual calendars. The development of the Lange 1 Tourbillon Perpetual Calendar launched in 2012 confronted them with the almost impossible task. That of harmoniously integrating the multitude of calendar indications into the dial architecture of the LANGE 1, without affecting the asymmetric arrangement of non-overlapping displays.

TOURBOGRAPH PERPETUAL “Pour le Mérite” (calibre L133.1); assembly of the programme wheel. It goes around once in four years and contains the information as to the different lengths of the 48 months in the four-year cycle.
TOURBOGRAPH PERPETUAL “Pour le Mérite” (calibre L133.1)

The earliest Lange pocket watches featuring a perpetual calendar as well as a moon-phase display date from the late 19th century and the Saxon manufacture can proudly add the Tourbillon to the list of complications integrated to a perpetual calendar watch.