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Precise and Perpetual – Resolving the Anomaly of Time
The reason for the complexity of our calendar, with its leap years and different numbers of days in the months, lies in an anomaly between the way we measure civil time and the cycles of the celestial bodies on which those measurements are based. Our 365-day calendar year is almost 6 hours shorter than a solar year (the time it takes for the Sun to return to the same position in the sky, completing a full cycle of seasons), which lasts approximately 365.2425 days.
Consequently, for watchmakers, a perpetual calendar is among the most challenging complications to master; a miniature mechanical computer, it must automatically adjust for months of different lengths and for leap years. Unlike a simple date display, which must be adjusted at the end of every month that doesn’t have 31 days, a perpetual calendar will not need any manual correction until 2100, which is a non-leap-year centenary. On centenary years that are also leap years it needs no adjustment.
Calibre 868, which powers the 2024 Master Ultra Thin Perpetual Calendar, was designed, produced and assembled in-house at Jaeger-LeCoultre; it evolved from the well-proven perpetual calendar movement launched by the Manufacture in 2013. In line with the Manufacture’s constant drive for technical innovation, the latest-generation Calibre 868 features a new escapement and pallets – reconstructed in a slightly modified shape, they minimise friction and thus consume less energy – and offers a robust power reserve of 70 hours. The long power reserve is particularly appreciated in a calibre with such complex indications and allows the wearer to set the watch aside for an entire weekend and wear it again on Monday without needing to correct any indications. When required, correction is done simply, via a single corrector set in the side of the case.
