Watchmaking storytelling: perpetual calendar watches

Gregorius XIII conceived on 1582 the Gregorian Calendar, the same calendar sill regulating our time. At that time, he did not reflected on the issues he would have created to watchmakers in the following centuries…

It was the XVI century when time measurement with a portable and adequately precise instrument became possible, but only at the end of XVIII Abraham Louis Breguet, the highest genius in watchmaking ever, was able to solve the complexity of Gregorian Calendar. On 1795 Breguet registered its patent for a “Quantième Pérpétuel”, meaning perpetual calendar, that was a pocket watch able to follow automatically the months flow distinguishing among different lengths (31, 30, 28 days and even 29, each four years.

This mechanical marvel was welcomed as a “pièce de maîtrise”, concept watch not conceived for high volume production, without any practical usefulness. Watches, at that time, were luxury watches very rare and intended only for a few distinguished people.

Today, the spread of watches with date indication always more precise and cheap created the desire of being able to have an always correct date indication without any manual adjustment. This launched again the myth of the perpetual calendar complication for wrist watches.

Perpetual calendar are included in the Patek Philippe catalogue since a long time: it was the first Maison who introduced it into the current production. A few later, other premium Companies, such as Vacheron Constantin and Audemar Piguet, contributed to a second youth of this fascinating complication, that ennobles many collections of Swiss watchmakers.

The perpetual calendar is, from a conceptual and technical point of view, easier than other complications to be added to wrist watches (such as the minute repetition), although is probably the most fascinating since it is so connected to continuous time flow. The heart of this watch is a small wheel making a turn each four years, indicating the months with 28 (or 29, in leap years), 30 or 31 days of each months. The perpetual calendar is usually combined with the automatic recharge movement, in order to avoid a frequent date, month and year re-setting.

At this point, could you say that all the issues connected to Gregorian Calendar have been solved? Unlikely, no. There is a codicil, a small and mostly unknown rule, that defines the secular years (1600, 2000, 2400) as leap years only if divisible by 400. This means that 2100, even though is divisible by 4, will not be a leap year because it is not by 400. In making a watch that is expected to remain useful through several lifetimes, Patek Philippe devised the secular perpetual calendar that keeps the full 400-year cycle of the Gregorian calendar. At the end of every century, the mechanism decides whether it is a leap year or not. This is done by one of the slowest mechanisms in horology – the star-wheel and its four-pointed satellite, which has three long points and one short point. The star-wheel goes round once every 100 years. At the end of each century, it carries its satellite past a peg, which gives it a quarter turn. For three consecutive centuries the long points of the satellite project to lift the lever so that it stops February on the 28th day. In the fourth century (the years 2000, 2400, 2800 etc.), the short point fails to engage the lever, and February is allowed to stop on its 29th day, denoting a leap year. This patent was granted when Patek Philippe created the Caliber 89.

Perpetual calendars, produced in few numbers each year, are very requested by lovers and collectors all over the world, gaining a watch that will follow the flow of all their life.

Talking about calendars, an interesting innovation was introduced on 1996 by Patek Philippe: the Annual Calendar, a mechanism able to distinguish among 30 and 31 days long months. This watch needs to be regulated only at the end of February, both in leap and regular years. This innovation has been very well accepted by the public, since allows to monitor the time flow during the whole year, with the exception of only one day, for a more affordable price compared to perpetual calendars.

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Il calendario perpetuo per eccellenza di Patek Philippe, ref. 5140. Ultrapiatto, automatico.

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Il calendario perpetuo istantaneo di F. P. Journe

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Da Vinci di IWC Shaffhausen dotato di calendario perpetuo

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Calendario perpetuo di Cartier, su cassa Rotonde, con le caratteristiche geometrie Cartier sul quadrante

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Uno dei due quadranti del Calibro 89, il supercomplicato di Patek Philippe dotato, fra le altre complicazioni, di calendario secolare

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Il calendario annuale Patek Philippe ref. 5396

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Lo Sky-Dweller di Rolex, calendario annuale che indica il mese con una finestrella sopra gli indici delle ore

Tags: Blancpain How does it work? Jaeger-LeCoultre Watchmaking technique Vacheron Constantin