During the 18th century, the production of astronomical clocks gradually gave way to that of clocks that indicated the date and phases of the moon. These early calendar clocks were of a simple type: at the end of each month lasting less than 31 days, the date hand had to be advanced manually. The addition to the movement of the complicated perpetual calendar mechanism, in which every four years the 29th of February is automatically recorded, has long been the dream of every watchmaker. The Quantième Perpétuel (perpetual calendar) displays the exact date by automatically taking into account the variable duration of the months and the leap year cycle. It also displays the day, the month and often the phases of the moon. To accomplish this feat of watchmaking, the movement must possess a mechanical "memory" of 1461 days, or four years. The ninth creation within the Octa collection, the Quantième Perpétuel by F.P. Journe with instantaneous release presents a highly original aesthetic, offering perfect legibility thanks to a very essential dial with large windows: two for the day and month calendar and two for the big date. The instantaneous strike is equipped with an ingenious system, designed to accumulate energy and release it instantly as the date, day and month pass, but also to slow it down at the end of its course. Unlike perpetual calendars that are often difficult to set, the Quantième Perpétuel F.P. Journe is very easy to use. All adjustments are made via the crown in 3 positions, except for the rapid month correction, which is carried out by a protected correcting lever concealed under the lug at 1 o'clock that facilitates adjustment over the 4 years, without a specific instrument. The passage of the months of 28, 29, 30 and 31 days takes place automatically with the recognition of the leap year, indicated in the centre of the dial below the hour and minute hands. The self-winding movement of the Quantième Perpétuel by F.P. Journe is crafted in 18-carat red gold, like that of all the brand's precision chronometers. It is built on the basis of the exclusive Octa 1300.3 calibre and equipped with the exclusive F.P. Journe off-centre rotor in 22-carat red gold, enabling optimised winding of the watch for a power reserve with retrograde indication of more than 120 hours. The new version of the Quantième Perpétuel is available in platinum or 18-carat red gold, with a diameter of 40 or 42 mm and a guilloché-worked solid silver dial with gold applied numerals.
