PERPETUAL CALENDAR
The perpetual calendar is designed to display the date on a dial, taking into account the varying lengths of months and years, including leap years. This sophisticated mechanism enables watches and clocks to indicate the correct date without manual adjustment, even over long periods. A perpetual calendar shows at least the date and month, but typically also includes the day of the week and moon phase. For improved legibility and to distribute the indications more clearly across the dial, one or more of these indications are sometimes displayed using a retrograde hand.
History and origins
The idea of the perpetual calendar complication dates back to the 18th century, although the concept of tracking the passage of days is as old as humanity itself. Earlier, watchmakers employed relatively simple mechanisms to display the date, but these systems required frequent human intervention, particularly to adjust the date at the end of 30-day months or in February.
The invention of the perpetual calendar is generally attributed to Abraham-Louis Breguet in the early 19th century. However, even before that, the first attempts at mechanisms capable of accounting for the irregularities of months and years began to appear in complicated watches from the 18th century. It was in 1820 that Breguet succeeded in creating a prototype that incorporated automatic date calculation, thereby revolutionising calendar mechanisms in watches.
How the perpetual calendar works
The fundamental principle of the perpetual calendar is to display the date while accounting for the different lengths of months and leap year. This mechanism relies on a complex system of wheels, pinions and levers that compute the exact number of days in each month and adjust automatically according to these varying durations.
Conclusion
The perpetual calendar stands as a testament to horological ingenuity and expertise, perfectly illustrating watchmakers’ ability to push the boundaries of mechanics to create timepieces that not only indicate the time, but also calculate the passage of days with remarkable precision. It remains today one of the most sought-after and admired complications in the world of watchmaking.