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Perpetual Calendars and Why We Love Them

For centuries, humanity has sought to make sense of the passage of time throughout the year and across the seasons. From the sundial and Greek clepsydra (or water clock) to modern wristwatches and atomic devices, we continue to develop ingenious ways to determine the day, date, and time with growing precision.

One of these methods is the perpetual calendar function, also known as QP (from the French quantième perpétuel).

Perpetual Calendars and Why We Love Them
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3 Types of Watch Calendars

Calendar complications for watches fall into three distinct categories: Simple or complete, annual, and perpetual. The simple calendar conveys the day and date and requires a monthly reset to account for the different number of days each month.

The annual calendar goes one step further by adding a lever to adjust for changes in days per month automatically. You only have to adjust this calendar watch once a year after February to factor in the leap year.

And then there’s the perpetual, which represents the longest-lasting and most accurate calendar complication with no adjustments needed except in non-leap years like 2100. The newest secular perpetual calendar complication even self-adjusts for these non-leap years, making watch adjustments unnecessary for centuries. A perpetual may also include other essential timekeeping information, such as religious holidays, seasons, tides, and moon phases.

A Brief History

The QP mechanism finds its roots in the creation of the Gregorian calendar in the late 16th Century. Up until 1582, yearly calendaring calculations determined a year to be 365 ¼ days long. As a result, the calendar should have stayed in line with the seasons by factoring in an additional day every four years (leap year).

But the math was slightly off. The time it takes for the Earth to orbit the sun is actually 365 days, 5 hours, 48 minutes, and 45.25 seconds. According to the Encyclopedia Britannica, those few extra minutes and seconds caused an estimated regression of about one day per century.

When Pope Gregory XIII introduced reforms to the Julian calendar, originally instituted by Julius Caesar a few decades before the advent of the Common Era (CE, also known as Anno Domini, AD), the Vernal Equinox was already off by about 14 days. To fix this, Gregorian mathematicians advanced the calendar ten days after October 4th, 1582. In true Rip-van-Winkle fashion, people went to bed that evening and woke up to find time had moved ten days ahead in one night.

Pope Gregory’s changes also stipulated that no century year would be a leap year unless it were divisible by 400. As such, most standard perpetual calendar watch mechanisms will need adjustment in 2100 since that will be a non-leap year. This means even if you don’t need to worry about it, your heirs will likely want to keep a Breguet watch repair pro on speed dial for that Classique 3787 you’re wearing.

How Perpetual Calendars Made It Onto Wrist Watches

Thomas Mudge, a brilliant English watchmaker responsible for creating the lever escapement, introduced the perpetual calendar function to the pocket watch in 1762. It wasn’t until 1889 that Patek Philippe filed a patent for the mechanism and then, less than a decade later, delivered it to customers in the form of a ladies’ pendant watch.

Patek rehoused the movement into a wristwatch case in 1925, thus becoming the first to deliver the function in a wrist-wearable format. Breguet would follow suit by designing its own QP watch mechanism in 1929.

In 1985, when mechanical watchmakers were being pummeled in the Quartz Crisis, IWC Schaffhausen’s head watchmaker Kurt Klaus developed a perpetual calendar module that you could control entirely from the crown. No more extra push buttons or complex directions to reset your watch if you happened to put it away for a few days and it needed a reset.

By taking the hassle out of the maintenance equation, watch owners found they could enjoy a high-quality mechanical timepiece and yet still have all of the quartz’s calendering and other functions. Thus, the IWC Da Vinci Perpetual Calendar 3750 was born, and it not only put IWC back in the haute horlogerie game but also revitalized overall interest in mechanical watches.

Why QPs Are Really ‘All That’ (and More)

You may not think a perpetual calendar is all that special, considering that any computer, smart device, or standard digital watch can make these calculations in nanoseconds. However, when you’re talking about a mechanical watch complication, there’s a lot more to it.

Mechanical timepieces utilize many tiny parts, including springs, screws, wheels, levers, and gears. Additional complications, such as a perpetual calendar, increase the number of pieces within a watch (typically anywhere from 50 to more than 200) and the complexity of its inter-connective operations. Owning a mechanical QP means you wear on your wrist the same kind of engineering excellence found in some of the world’s greatest machine inventions.

A Patek Philippe with a high-end complication like the perpetual calendar can take more than two years to make and contain over 500 moving parts. While pricy luxury watch movements can sometimes comprise thousands of components and dozens of complications, the timekeeping industry continues to focus some of its energies on designing perpetuals with fewer pieces.

Why? Mechanisms without hundreds of constantly-rotating parts naturally create less internal friction and may prove more reliable. They also could save you a bundle on trips to the watch repair shop for regular maintenance. A few examples of doing more with less are Frederique Constant’s Highlife Perpetual with an automatic movement of 191 total parts, and the industrial-looking Ochs und Junior Perpetual Calendar, which only uses nine components for its QP function.

Complications Come with a Price

Due to its superb engineering, a QP watch will often cost you tens of thousands of dollars, regardless of how many parts it has. Take the Ochs und Junior – it retails for more than $23,000. Granted, that may seem like little when compared with the Patek Philippe Grand Complications 5236P In-Line perpetual, which costs over $140,000.

The Frederique Constant Highlife Perpetual, priced at just under $10,000, is one haute horlogerie option for those with a more limited budget. You can’t beat that price for a new, high-quality mechanical watch with a perpetual calendar function. Other lower-priced choices include older perpetuals, like the Piaget Gouverneur, Jaeger-LeCoultre Master, or IWC Portofino, which you can find in the gray (secondary) market.

Sure, you can purchase a great Seiko quartz or Citizen Eco-Drive perpetual calendar watch for under $1,000, but where’s the fun in that? If your objective is simply to keep the correct date and time for the rest of your life, you can use your smartphone. But if you want to own a hand-finished, precision-engineered piece of watch history (not to mention a great conversation starter), consider investing in a mechanical QP. You’re guaranteed to smile every time you look at your wrist.