The idea of “forever” has always had a certain romanticism about it — obviously out of reach, yet like a forbidden fruit is ceaselessly pursued as a hallmark of excellence. But the only constant is change, and the challenge in defying the limits of time has been undertaken by none other than the guardians of time themselves. Called a “perpetual calendar”, this grand complication is by far one of horology’s most practical creations, and also one of its most ambitious, giving timepieces the ability to correctly display the date for a century while taking into account the different lengths of the months and leap years.

You may have noticed that many watches usually sport an aperture displaying the date, some even the day of the week. Perpetual calendars can be distinguished by not only showcasing those, but also the month and a leap year indication.

The traditional timekeeping function of these watches work in tandem to a series of algorithms that have been translated into a plethora of additional gears that turn at varying lengths of time. The perfectly synchronised dance promises an accuracy of an entire century, assuming you keep it constantly wound (consider a winderif your wallet can indulge you with variety). Contrary to popular belief, however, perpetual calendar don’t exactly run with accuracy until the end of time.

Counting the days

The MB&F Legacy Machine Perpetual.

Perpetual calendars are essentially mechanisms replicating four-year cycles based on the Julian calendar. This calendar sees an extra day in February every four years when Julius Caesar assumed a full year should be 365.25 days, when in actual fact he was 11 minutes off. To offset a relatively sizeable difference in the future — and to align the Earth’s revolutions around the sun — Pope Gregory XIII introduced the Gregorian calendar, dictating any year divisible by four to be a leap year, unless that year is also divisible by 100. However, if that year is also divisible by 400, a leap day is added regardless.

In modern day context, this means that the next time your watch requires adjustment is in the year 2100, on March 1st. Don’t forget to leave your grandchild a note for this.

Time immemorial

The perpetual calendar has become a true test of mechanical understanding for watchmakers over centuries, but Thomas Mudge invented the mechanism first in the 18th century. Patek Philippe caught up only almost a century later, filing a patent for its pocket watch-designed mechanism in 1889. 36 years later, the Swiss marque outfitted a pendant watch movement into a wristwatch for Thomas Emery, an American who was quite the fan of the brand. This was the first known perpetual wristwatch ever made.

Breguet jumped on the bandwagon with the Breguet no. 4244 in 1929, likely to be the first wristwatch to be powered by a perpetual calendar movement made specifically for a wristwatch. Sold to Monsieur Jean Dollfus — of whom the watch is now affectionately nicknamed after — the watch hasn’t made the news since it exchanged hands at a Christie’s auction in 2011 for more than S$656,000.

Now a staple in any respectable watchmaker’s lineup of grand complications, the perpetual calendar has become an art in itself to execute. While Blancpain, Patek Philippe, and Vacheron Constantin are classicists in their presentation, manufacturers like Cartier and MB&F push the envelop just a little further to marry astronomyand horology unconventionally.

Breaking the mould

The Cartier Rotonde de Cartier Astrocalendaire.

Here, the Cartier Rotonde de Cartier Astrocalendaire ditches the usual apertures and subdials for a mesmerising multi-tiered styled display. The Roman amphitheatre-esque presentation — perhaps an allusion to the calendar’s Roman beginnings — dramatically encircles a flying tourbillon with each ring indicating the day of the week, the month, and the date. The leap year here is visible through the transparent caseback via a hand on one of the bridges.

The Franck Muller Aeternitas Mega 4.

Then there’s the Franck Muller Aeternitas Mega 4 and its almost mythical capabilities of having a calendar function that’s not only calibrated to calculate leap years, but also the non-leap years every 100 years, and the leap years on 400-year cycles. A 1,000 year calendar indication sits just below the centre hand, accompanied by more than two dozen more grand complications such as a grand and small Westminster chime striking-work and equation of time.

Perpetual calendars are grandiose undertakings that are truly the apotheosis of the art of watchmaking. Unlike complications such as the minute repeaterand tourbillon, which saw theirpracticality wane with technology, perpetual calendars are still highly relevant in modern times — even if only for the next few decades.

Shatricia Nair
Senior Writer
Shatricia Nair is a motoring, watches, and wellness writer who is perpetually knee-deep in the world of V8s, tourbillons, and the latest fitness trends. She is fuelled by peanut butter and three cups of coffee a day.