EASY YEARS AHEAD
Cartier has managed to create the easiest time and calendar change in a mere instant.
immediately stands out. The sub-dials and windows through which it is often presented occupy most of the watch face, marking the timepiece as a work of technical mastery. To better appreciate this complication, we need to understand its purpose. An astronomical year is the time taken for the earth to complete one orbit around the sun, and takes 365.24 days. However, for daily usage, there is a requirement to have round numbers and this prompted the Roman emperor Julius Caesar to institute the leap year in 46BC. Thus, the Perpetual Calendar challenges watchmakers to follow the stride of time across day, week, month and year through the decades with no adjustment needed, while accounting for leap years.
How have traditional watchmakers accomplished this feat? It helps to understand that the principal component of a perpetual calendar watch is the month cam. Think of this as a disc that has been fixed to the underside of a larger rotating wheel. It has seven ridges (for months with 31 days), four dents (for months with 30 days), and a larger dent with an additional rotating piece for February. This is essentially the mechanical memory for the perpetual calendar, and is joined to the day, date, year and other mechanisms via a series of wheels, discs, levers and pawls (fingers which engage the wheels) which are set at different heights so as to rotate the various discs at their respective times. A full explanation is out of the scope of this article but the reader can imagine that with multiple mechanisms involved, any adjustment would have to be made via multiple pushers on the watch case.
The Rotonde de Cartier Astrocalendaire watch departs from this. The Perpetual Calendar displays are arranged three-dimensionally in concentric levels; day is indicated on the first, month on the second, with the outermost circle showing the date. Each tier has a moving blue window which directs the wearer’s eye to the applicable marker at the time. Finally, a hand on the back of the watch informs whether it is a normal or leap year. Partially patented, the gear train system of the Astrocalendaire’s 9459 MC movement replaces the traditional lever and spring mechanisms with a gear train mechanism that significantly reduces the risk of damage should the watch ever be over-wound.
Cased in platinum and wound automatically from its large rotor (with a 50 hours power reserve), the Astrocalendaire’s design represents great technical ingenuity. The design of a tradition perpetual calendar prohibits any manual correction several hours before and after midnight at the risk of breaking the mechanism. In addition, when making adjustments to the watch, the usual four push-pieces on the side of the case are hard to navigate and never clearly identified. The Astrocalendaire eliminates this problem by incorporating a setting system which utilizes the crown to control the date and month indicators along with the usual hour and minute hands. Adjustment of the watch is made even easier with the possibility of correcting the various mechanisms forwards and backwards. This has hitherto been a strict no-no for most mechanical watches.
Incorporating the tourbillon complication which offsets the effects of gravity on the watch’s movement and certified Poincon de Geneve, the Rotonde de Cartier Astrocalendaire easily distinguishes itself from the other watches with the Perpetual Calendar complication. While it flawlessly measures time through future decades, it is most certainly an innovation for the present.