To those dedicated to the concept of timekeeping accuracy, it must seem disheartening that after all the brilliant inventions in the world of horology over the past century and a half, the sundial remains the most accurate form of real time measurement – at least if you want to track true solar time. A sundial measures time according to the current position of the sun, by which the length of a day can vary by up to nearly 17 minutes from average or civil time. The difference is called the equation of time, and for the diehard fan of real time, the equation of time complication is the only way to track it. One of the things that keeps this complication valuable and collectible is its rarity: while every brand makes a tourbillon, only a handful make an equation of time, among them Vacheron Constantin, Patek Philippe, Franck Muller, Blancpain, Zenith, Panerai, Breguet, Bulgari, Jaeger-LeCoultre, Ulysse Nardin and Audemars Piguet, whose spectacular Royal Oak Equation of Time is an outstanding recent example.
The equation of time, not an isolated function
For practical reasons, mankind has divided each year into 365 and a quarter days, each day into 24 hours, and the hours into 60 minutes each. However, because the Earth’s orbit is elliptical rather than circular, the time in relation to the Sun varies daily. It is exactly twenty-four hours long on only four days: April 15th, June 14th, September 1st and December 24th.
Because these variations occur identically on the same dates, they can be programmed into a watch movement by means of a cam making one complete rotation a year. The cam is often linked directly to a perpetual calendar so that the display of the equation of time always corresponds to the current date.
The equation of time is rarely seen as an isolated function; as one of the great feats of horology, it is often combined with others in a grand complication. There are different ways to show the equation of time. Most watches use a hand sweeping a subsidiary dial or arc, graduated from 16 to +14 minutes. Others have a running equation of time, which consists of a second minute hand that simply runs according to solar time, making the difference readable at a glance. The equation of time is a highly collectible function, not just because few make one but because it is usually made in a limited edition or as a one-off.
A true complication
“As the pool of watch collectors grows, we’re starting to see sub-genres of collectors,” says Michael Friedman, horological director of Antiquorum. “Equation of time watches have the potential to attract more enthusiasts because they’re not being over-produced, which makes them rarer. There will always be interest in the tourbillon, just because it is so visually interesting, but the equation of time is a true complication, and that will always appeal to collectors who take an interest in the broader, philosophical aspect of timekeeping. It’s a reminder that there is human time and then there is celestial time; it explores the relationship between time and space.”
While tourbillons have been presented in every post-modern, space-age configuration possible, the equation of time tends to be manifested in the dignified manner of traditional watchmaking, with engraving, enameling, porcelain dials, applied Roman numerals, etc., which enhances their currency as artifacts of timekeeping. A modern example is the recently introduced Vacheron Constantin boutique version of its Patrimony Traditionnelle Calibre 2253. It is crafted to the exacting new Geneva Hallmark standards, with superior finishing both inside and out. Made as a one-off for the brand’s Madison Avenue boutique, the Calibre 2253 houses not only an equation of time but also a tourbillon as well as sunrise and sunset indicators, perpetual calendar and a power reserve indicator. “It is the combination of all these complications that make this watch exceptional, and thus challenging from a technical point of view, right from the conception to the realization,” says Hughes de Pins, President of Vacheron Constantin North America. He adds, “The rarity of such a timepiece makes it very appealing for the most knowledgeable collectors.”
One of the most desired high complications
The new Patrimony Traditionnelle Calibre 2253 is exceptionally decorated in the tradition of the classic Patrimony collection, which also houses the brand’s most impressive complications. The case is in 5N rose gold, contrasted with a light grey dial. Sunrise and sunset are indicated at 8 o’clock and 4 o’clock on the dial, while equation of time is shown on an index between 10 and 11 o’clock. The grey hands of the subdials offer a subtle contrast to the rose gold central hour and minute hands; on the platinum version, blue subdial hands are paired with white gold central hands for a more striking contrast (the Calibre 2253 was first introduced in 2010 in a platinum limited edition). The ultimate flourish of this beautiful watch, however, and what makes it really stand apart from the original, is the hand engraving on the flank of the case. The scrolling, which runs the full circumference of the case, mirrors the spiral wave-like pattern of the frieze on the exterior of the Madison Avenue boutique (formerly a David Yurman boutique). The engraving makes the 9.60mm thick case seem less hefty: the watch has two pairs of coupled barrels which ensure a power reserve of 14 days but add a certain thickness to the watch. The movement is manual-wound. It is one-of-a-kind and retails for USD 541,900.
The equation of time is not an essential function like a perpetual calendar, although one could easily argue that neither is the tourbillon, which makes very little difference to the accuracy of today’s advanced movements. However, the equation of time does have true currency as a collector’s complication. “The inspiration for the equation of time is more conceptual than practical,” says de Pins. “But the equation of time is considered among watch collectors as one of the most desired high complications.”
Recently at a Sotheby’s auction in London, a George Daniels grand complication, circa 1982, with equation of time, tourbillon, minute repeater and perpetual calendar sold for approximately USD 2.1 million. Dubbed the “Space Travellers’ Watch” it was in perfect condition, with beaded and polished gold case, applied Roman numerals and a traditional layout of functions, dominated by the equation of time index. “Like the minute repeater and the perpetual calendar, the equation of time is rooted in the history of watchmaking,” says Michael Friedman. “It’s a reflection of the advancement of precision.”