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Equation of Time Watches

Christopher Beccan
Oct 25, 2016
Blancpain Le Brassus Equation du Temps Marchante PT

Time is a funny thing; we humans go about our lives here on earth adhering to the time we see on our watches and take it for gospel. While it’s not a million miles out, it’s not quite correct either. You see, there is a thing called “apparant solar time,” which doesn’t perfectly line up with the time we follow day-to-day. There is a complication that shows us the difference, the so-called Equation of Time, but what exactly is it?

The Equation of Time is the difference between solar mean time and apparent solar time, and over the many years of man’s fascination with said time, a complication has been developed to display this anomaly. The equation of time complication on a watch displays the difference between the length of an actual solar day and the mean solar day. A day is calculated, astronomically, as the amount of time it takes the Earth to revolve around itself – a solar day. On average, this takes around 24 hours, however, due to the Earth’s peculiar orbiting pattern, as well as the tilt of its axis relative to the plane of its orbit, it can be as much as a quarter of an hour more or less on any given day. Put more simply, it is the difference in time you’d see on your watch and that on a sundial; this is what the equation of time complication displays at any given time of day. That said, there is one caveat: This difference in time has to be calculated at the specific owner’s location, making each piece that can do this somewhat unique.

Same Complication, Very Different Watches

There are a few timepieces out there that can do this, so we’ve decided to highlight some that we think are just downright cool.

Audemars Piguet Royal Oak Equation of Time

This masterpiece measures an extremely modern 42 mm in diameter and houses the complicated movement 2120/2808, which consists of no less than 423 parts. What does it do for you? Well, of course it can display the time (hours and minutes), but on top of that, it displays the day, leap year, equation of time, the astronomical moon phase as well as the time of sunset and sunrise at the wearer’s location. While the perpetual calendar and sunrise/sunset complications probably don’t need elaboration, I think it is important to mention that the combination of all these features makes this one seriously complicated timepiece – and to think that Audemars Piguet managed to do this without losing the original 1972 octagon-shaped case design.

That said, AP also houses this 2120/2808 caliber in a more classically styled timepiece in their line-up: the Jules Audemars round case. Personally, I think the equation of time looks more at home in this piece, yet it still works very well in the Royal Oak. All in all, this is a true demonstration of masterful watchmaking from Audemars Piguet.

Girard Perregaux 1966 Annual Calendar & Equation Of Time

Perhaps one of the most interesting, simple, and dare I say odd equation of time wristwatches is the Girard Perregaux 1966 Annual Calendar with Equation of Time. I say odd because the pairing of these complications is just so different to anything else available on the watch market. Launched in 2009, it features an annual calendar that may be corrected by using the crown in both directions, thereby making correction easier and leaving the case band free of any recessed pushers. The date, month, equation of time, and small seconds each feature a different hand shape. The watch is housed in a 40-mm white gold or pink gold case and at the heart of this timepiece is the self-winding GP033M0 movement with a 46-hour power reserve.

In 2013, it was followed up with the release of the 1966 Minute Repeater, Annual Calendar and Equation of Time (limited to 15 pieces), which combines the three named complications on a silvered sunburst-decorated dial with solid gold appliqué hour markers and diamond powder-coated pink gold hands. The timepiece is equipped with a 42-mm pink gold case that is water-resistant to 30 m, a brown alligator leather strap with pink gold folding buckle, and the manual-winding Girard-Perregaux E09-0003 movement with a 4-day power reserve, which is visible through the sapphire crystal case back.

Blancpain Villeret Equation du Temps Marchante

Another timepiece that displays this accurate orbit of Earth is the Blancpain Villeret Equation of Time. When Blancpain introduced the Equation at the 2004 Basel fair, it marked a first in watchmaking history: The wristwatch not only displayed a plus/minus expression of equation of time, but also a running equation of time minute hand that directly showed solar time. Made in a limited quantity in both platinum and rose gold, it has been decked out with all the indications one would require. It is powered by the self-winding Calibre 3863 movement, which consists of slightly fewer parts than the AP mentioned above: 397.

The white grand feu enameled dial displays the equation of time via an indicator at one o’clock as well as a perpetual calendar and moon phase via a retrograde indicator at eleven o’clock. At six o’clock, there is a circular cutout in the dial that reveals a small part of the movement. This is actually a view of the equation of time cam and the ratchet that rides upon it.

Panerai Luminor 1950 Equation of Time 8 Days

The strange thing about this next timepiece is the fact that this watch manufacturer is well known for making large sports watches, yet they’ve come up with a way of displaying the equation of time in a very intuitive and simple format. In 2015, Panerai introduced the Luminor 1950 Equation of Time 8 Days Acciaio. While the equation of time complication is rarely seen on Panerai watches – the last time being the Panerai L’Astronomo or PAM 365 from 2010 – the watch works aesthetically. The dial layout is atypical of Panerai, but if you look closer, you’ll notice the inclusion of an equation scale that sits just below the center axis that accounts for plus or minus 15 minutes per day. However, you’ll also notice that there is a second subsidiary dial adjacent to the running seconds. This displays the date and month of the year.

Beneath the dial of the Panerai Luminor 1950 Equation of Time 8 Days Acciaio is the new P.2002/E movement, which in turn is based on the P.2002. Like all in-house manufactured Panerai movements, the P.2002/E is quite large and measures approx. 31 mm wide and 8.3 mm thick. It is made up of 328 parts and boasts no less than an 8-day power reserve.

Breguet Classique Complications 3477

It would be impossible to mention a complication such as the equation of time and not mention one of the true masters of watchmaking: Abraham-Louis Breguet. During his lifetime, Abraham-Louis Breguet created some extraordinary watches displaying equation of time. However, since that time, Breguet has invented and patented a perpetual equation of time mechanism that is coupled with a perpetual calendar. Both are designed to operate without correction for over two centuries, which is nothing short of remarkable.

The 35.5-mm case of the Classique Grande Complication with signature fluted case band houses the self-winding Calibre 502DPET, which is visible through its sapphire crystal case back. The silvered gold hand-engraved dial features minutes, hours, and months at its center, day of the week at twelve o’clock, date at six o’clock, leap year at eight o’clock, power-reserve indication between nine and twelve o’clock, equation of time between twelve and three o’clock, and the iconic Breguet blued steel open-tipped hands.

These are just a few hand-selected pieces that showcase this incredible complication. While it’s admittedly not something that all will need or even use, it’s nice to know that these little timepieces we strap to our wrists afford a glimpse into the solar system.

Christopher Beccan
By Christopher Beccan
Oct 25, 2016
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