Can a perpetual calendar watch last for ten thousand years?

　　When it comes to mechanical watches, lacking a compiler to store the calendar system, master watchmakers have no choice but to use precise gears to "remember" special years within 100. So can a perpetual calendar watch really be used for ten thousand years?

　　What is a perpetual calendar?

　　Do not take this name literally—a perpetual calendar watch cannot display dates for ten thousand years. The English term is 'Perpetual Calendar', which essentially means an eternal calendar. It can recognise the current month, the current year, and even whether the current year is a leap year. It will automatically insert the twenty-ninth day into February during a leap year 2. Therefore, as long as the watch is running well, the only time you need to adjust the date is at the end of February in years that are not leap years 29, such as the year 100 2 2100.

　　Who invented the perpetual calendar?

　　According to literature records, the French philosopher Diderot mentioned in an encyclopedia compiled by him in 1765 a calendar watch named "Constant" made by the Swiss watchmaker Ferdinand Berthoud. Subsequently, another 18th-century master watchmaker, Jean Antoine Lepine, recorded that a master named Lepine had once presented King Louis XV with a grand complication pocket watch integrating a minute repeater, equation of time, and perpetual calendar functions. It is surmised that Breguet, the inventor of the tourbillon, may have studied under Lepine for a period of time, which could be the reason he invented the world's first perpetual calendar pocket watch.

　　The movement design of a perpetual calendar is not overly complex, incorporating a unique star-wheel structure, convex-month structure, and a Maltese cross leap-year counter, among others. These structures were already widely known as early as the 19th century. However, the first perpetual calendar wristwatch was crafted by Patek Philippe in 1925 and sold to Mr Thomas Emery in 1927. It simply utilised a ladies' pocket watch movement completed as early as 1898. This movement, bearing the reference number 97975, could not only display the date, day of the week, and month, but also featured a moonphase complication. All the hands on this watch featured instantaneous jump mechanisms, which remain astonishing even today.

　　A decade or so later in 1941, while the world was still engulfed in the flames of war, Patek Philippe launched the world's first mass-produced perpetual calendar wristwatch, PP1526.

　　How to maintain a perpetual calendar wristwatch?

　　Due to the inherent arrangement and combination of the mechanical components within a perpetual calendar, adjusting it after it has stopped running is quite complex. Adjusting traditional perpetual calendar watches relies on various correction push-pieces located on the side of the case, which require specialised tools to operate. Nowadays, aiming for convenience and practicality, some watch models adopt the simplest adjustment method: simply pull out the crown and adjust different parameters such as the calendar and day of the week at different positions. If you are afraid of the hassle, you can take it to a watch shop for adjustment. However, a true watch enthusiast will never let a perpetual calendar watch stop running; if left unworn for long periods, it is placed in an automatic watch winder.