As timepieces with perpetual calendars again in 2016 prepare to demonstrate their capabilities, the new A.Lange & Söhne Tourbillon Perpetual Calendar is set to do so for the first time in its classic Lange 1 dial layout set into a white gold case. Previous models have featured rose gold cases or have been platinum limited editions.
The mechanism is designed such that a first one-day correction is not needed until the year 2100. That year, our relatives will relax: the Gregorian calendar actually omits the leap year.
But A. Lange & Söhne chose a different method. The German company placed the month indication on a large circumferential ring that rotates about its center axis once a year in twelve 30-degree steps. In its own technical review, the company explains that the display is endowed with recesses of different depths for the individual month durations and also takes account of leap years.
All displays on this perpetual calendar switch forward instantaneously, using up a force that had been gradually built up during 24 hours. 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. Because of these storage devices, the switching process does not affect rate accuracy.
All true perpetual calendars attempting to perform this feat must not only correctly transition from February 28 to February 29, but then also jump directly to March 1 at the end of the day. This may sound simple, but as A.Lange & Söhne reminds us, it is a formidable technical challenge. It requires the development of mechanical gearing that maps the different durations of all 48 months across the entire four-year cycle. Typically watchmakers do this by creating a wheel with 48 teeth in which the durations for each month during a four-year period are permanently stored in the form of gaps that have different depths.
Price: Approximately $345,000