What a difference a day makes. Every four years we have a day added to our calendar, creating a leap year. A leap year is defined as a year when an extra, or intercalary, day is added to the end of the shortest month, February. That extra day, February 29, is the leap day. A leap day is like a special bonus – an extra day to get things done, to experience life, and to make others happy. As lovely as the extra day is, it can pose some challenges. Calendar designers need to factor in that extra day, lest they get the entire year wrong. Corporations have to note the extra day too, and how it affects their production cycle. Watchmakers also take note of the leap year, particularly when they are working on a perpetual calendar complication.
A. Lange & Söhne has launched eight watches since 2001 that factor this special day into their perpetual calendar mechanism. Recently they brought us the LANGE 1 TOURBILLON PERPETUAL CALENDAR. There is a lot going on in this watch, having both a tourbillon and a perpetual calendar complication. Let’s focus on the perpetual calendar for now. A perpetual calendar adjusts automatically for months with different lengths, and typically uses a programme wheel with specific notches and steps. The notches for February are the deepest, save for one, which is meant for the leap year. The Saxon manufactory has created a new approach though.
The innovation developed by A. Lange & Söhne for the Lange 1 Tourbillon Perpetual Calendar involves a patented peripheral month ring and a completely new type of month display. This replaced the notched wheel but also brought with in the need for further research. They needed to find a way to rotate the new month ring and switch to a new month at the same time.
They explain it best, “The month ring is driven via its internal gearing. It rotates around 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. In February, an extender of the sampler lever contacts a cam beneath the leap-year disc. This tells the mechanism whether it is a common year with only 28 days in February or a leap year with 29 days.”
A. Lange & Söhne is no stranger to creation though, and they have 64 manufacture calibres tucked under their horological belt. Their desire to continually improve and innovate is what makes their watches so impressive. And why we keep wanting more of them.