Would it surprise you if we said the Jaeger-LeCoultre Polaris Perpetual Calendar is actually a type of computer? Well, strictly speaking, it is a miniature mechanical computer for the wrist that’s designed to provide not just the time but also the day, date, month, year, leap year, and phases of the moon. Sure, it doesn’t come with a heart rate monitor or connect wirelessly to your smartphone, or include everything except the kitchen sink. But consider this: It will perform this given task quietly, dutifully, consistently, unwaveringly, beautifully, perpetually and accurately, needing no corrections whatsoever until 2100. That’s the year 2100 mind you, not after 2100 hours, and it never needs charging or never runs out of juice, which is a huge win in our books.
Indeed, the perpetual calendar is one of mechanical watchmaking’s many great technical marvels. Complex, useful and prized by watch collectors, it is also one of the earliest horological complications invented in 1762, by prominent English watchmaker Thomas Mudge. You can see Mudge’s invention in pocket-watch form at the British Museum today. Infuriatingly complicated to produce, the perpetual calendar takes a watchmaker many years to fully master. The reason for its complexity stems from the anomalies of the universe as well as the way humans perceive time.
What makes a perpetual calendar superior to a regular calendar or even an annual calendar lies in its ability to track the passage of time with utmost precision, taking into account not just what month it is, but which months have 30 or 31 days. When February comes around, it can track if it will be a 28- or 29-day month. However, it’s not as straightforward as it sounds. Mostly it alternates between 30 and 31 days, but then you have July and August which both have 31 days, and there’s more.
Everybody knows that a full calendar year lasts 365 days. However, that is almost six hours shorter than an actual solar year, which is the exact time taken for Earth to orbit the Sun. This method of accounting would give us an error of one day every four days, which was why in 46 BC the Emperor Julius Caesar decreed to add an extra day to February every fourth year. But that solution alone would overcompensate the error by one day every 100 years. So by 1582 Pope Gregory XIII reformed the Julian calendar such that leap years occur once every four years, but if the year is divisible by 100 it is not a leap year, and if it is divisible by 400, then it is too a leap year. It is the Gregorian calendar which prevails throughout much of the modern world to this day.
Jaeger-LeCoultre’s journey with perpetual calendar timepieces began towards the end of the 19th century, shortly after the manufacturer gained worldwide acclaim for its numerous calibres and inventions. They advanced mechanical watchmaking with innovations such as the millionometre, the first instrument capable of measuring the micron. Given the immense number of additional wheels and levers required for this complication, miniaturising it from pocket watch to wristwatch was no walk in the park. But Jaeger-LeCoultre’s reputation as a movement and complications specialist allowed it to present its first perpetual calendar wristwatch as early as 1937, and to create some of the most innovative perpetual calendar complications in modern watchmaking. The four-sided Reverso Hybris Mechanica Quadriptyque of 2021, for instance, pushes timekeeping to never-before-seen limits.
For 2022—a year themed Stellar Odyssey by Jaeger-LeCoultre— the manufacturer introduced a new and improved perpetual calendar that reveres technical functionality as much as visual clarity. The Polaris Perpetual Calendar is the first model within the sporty Polaris family to be endowed with this fascinating complication, which meant it was the perfect opportunity for Jaeger-LeCoultre to present an upgraded version of its classic perpetual calendar calibre 868. And the Polaris Perpetual Calendar doesn’t disappoint in terms of fresh upgrades.
Among the usual improvements keeping it abreast of the latest technical innovations, the new calibre 868AA proffers increased power reserve to 70 hours, as well as the addition of a retrograde display of Southern hemisphere moon phases to accompany the traditional display of Northern hemisphere moon phases. Most importantly, the Polaris Perpetual Calendar allows one special feature found in few other perpetual calendars: an inner rotating bezel which offers an extra practical function of measuring elapsed time.
Meanwhile, its most surprising technical feature is as essential as it is elusive. If you knew anything about perpetual calendars, you’ll know to avoid tampering with the movement while the date mechanism is in transition. In this watch, a small security indicator at the centre of the dial shows red between the hours of 2000 and 0400, reminding the wearer not to make adjustments to the time and calendar indications during this period. That’s hella clever for something that’s not a smartwatch.