Additional Information A recent invention in the world of watchmaking since it was only perfected just under 15 years ago, the annual calendar quickly became the last word in terms of date display for watches intended for everyday use. Flexible to use and capable of being adjusted without needing to be re-set, this mechanism had until now failed to find its place in the Cartier collection. By incorporating it into the case of the Rotonde de Cartier watch, the team responsible for developing new calibres at the Manufacture has tried to satisfy watch lovers’ aspirations to have calendar information that is full and accurate throughout the year displayed on the dial.

A simple date function, or in other words a mechanism that enables the date to be shown in an aperture or at the tip of a hand, needs to be adjusted by hand at the end of each month with 30 days (i.e. with an even number of days) so as to ensure that the watch is in line with the calendar. This adjustment, easily carried out but frequently forgotten, may cause small errors on a month-by-month basis that need to be rectified manually.

This need to override the mechanical system by turning the winding crown to remove the number 31 and replace it with 1 in actual fact soon becomes an irritating chore. This is why the perpetual calendar mechanism was invented by watchmakers in the 18th century, enabling accurate calendar information to be displayed on dials, without the need for adjustment, for as long as the timepieces concerned remain in working order. Fascinating as these instruments are for their numerical memories, their owners are sometimes caused difficulties if ever these watches stop working for a prolonged period. The reason is that readjusting the calendar displays of these highly sophisticated models always requires numerous operations that sometimes oblige the watch owner to have recourse to a specialist.

To avoid these constraints when starting a watch, the Manufacture Cartier movement design team has perfected a reliable, efficient and sturdy mechanism for the Rotonde de Cartier Annual Calendar model that enables the date to be adjusted automatically at the end of the month (distinguishing between months with 30 or 31 days) and also displaying the days and months throughout the year, without requiring manual adjustment except in the case of the passage from 28th or 29th February to 1st March. The brand new Manufacture 9908 MC calibre is distinguished by a setting mechanism that enables the totality of a watch’s annual calendar information (day, date and month) to be controlled through the winding crown. This simple setting system, devoid of any kind of correcting device on the case, offers maximum ease of use on a day-to-day basis.

The Rotonde de Cartier Annual Calendar model, Cartier has chosen to incorporate an annual calendar mechanism directly into the plate of the 1904 MC calibre. This solution, particularly appreciated by lovers of fine watchmaking, was arrived at thanks to numerous tests to allow for the large date display with two independent numerals at 12 o’clock and the rapid setting of the different displays of the annual calendar through a cascade control process operated by the winding crown. This refined movement, highly original and developed entirely in-house, incorporates a number of important features, including a semi-instantaneous mechanism for converting the large date into two independent numerals (over a one-hour conversion period) so as to ensure the maximum chronometric stability for this paragon of fine watchmaking. In this system, the four-branched star-wheel corresponding to the tens column is turned by the catches located on the large unit disc. This unit disc – at the very heart of the calendar system – also holds another secret: it carries within it a simple and intelligent mechanism which, thanks to a cam bearing a memory of the months incorporated directly into the lightened rims of the units of the date device, makes it possible to display without any possibility of error the months having 30 or 31 days, once the current month has been set.

This mechanism of irreproachable efficiency is programmed to take into consideration the length of the months with an even or odd number of days, except in the case of February (with 28 days, or 29 once every four years). It is completely incapable of being de-indexed even if subjected to a severe impact. This automatic annual calendar, for which Cartier designers succeeded in devising the operating system by combining the presentation of the date with a day and month display using a dragging hand mechanism, undergoes strict testing so as to withstand all the requirements of everyday life.