This season, the tireless horological ingenuity that Stephen Forsey and Robert Greubel inject into their watchmaking finds a new episode in QP à Équation, now with a warmer appearance. It is the QP à Équation, a perpetual calendar with equation of time display, now dressed in the cozy shades of the red gold and a warm chocolate dial.

When Greubel Forsey debuts a “new invention,” the world stops on its tracks to pay attention. Since the irruption of this firm in 2004, Greubel Forsey has reestablished the parameters of extreme horology, not only because of the apparent technical richness of its pieces, but also because of the guiding concept that gives life to each one of them: the search for maximum precision. That’s why when the QP à Equation (“QP” is quantiéme perpétuel, French for “perpetual calendar”) debuted in 2017 in its white gold version, it caught the eye and sighs of us all, for it was the embodiment of Forsey and Greubel’s vision of what a perpetual calendar, easy to read and maintain, should be. And, to boot, it also included the coolest and most underrated of complications: the equation of time.

At the heart of the seventh invention of the QP à Equation lies the Mechanical Computer, a 25-component module that redefines the way information is presented with regards of the astronomical clocks of yore. Using a coaxial gear train and information-reading combs, the system constantly “reads” the position of the wheels to display time as clearly as possible. For the equation of time, the Mechanical Computer also drives a series of sapphire discs that show in real time the difference between civil time —the 24-hour time that governs you and me— and solar time —which is the actual length of each day and varies throughout the year as a consequence of the elliptical translation that the Earth makes around the sun. This time difference can go from -14 to +16 minutes and is zero four times a year.

Essential to the watch was to simplify the way all indications can be corrected by turning the two-way crown. Despite its many functions and displays, plus its combination of three patents and two inventions, the Greubel Forsey QP à Équation is still as easy to adjust as a simple calendar.

The dial-side of the QP à Équation shows the most sought-after information: leap years, 24 hours/day and night, day of the week, date, time and the 72-hour chronometer-grade power reserve. Three openings aligned on the sub dial at 3 o’clock give an unambiguous indication of the day, date and month for greater visual ease. The very big date makes the readability perfect, and the rest of the calendar elements are quite easy to find and read, too. On the opposite side of the movement, the watch displays the seldom required information, such as the aforementioned equation of time with the months, seasons, solstices and equinoxes, as well as the year.

Greubel Forsey QP à Équation
Greubel Forsey QP à Équation

The chronometric performance of this watch is based on Greubel Forsey’s third invention: the Tourbillon 24 Secondes, which uses a rapid rotation speed and an inclined angle to solve the problem of critical positions of the oscillator in relation to gravity. A 25° angle to the vertical axis and the rapid swirling of the tourbillon cage significantly improve the timing performance of a system containing a single tourbillon, especially in stable positions.

This new version of the QP à Équation maintains the 43.5 mm case size with a thickness of 16 mm. The chocolate-colored multi-level gold dial of this millesimal edition watch contrasts harmoniously with the 5N red gold case and beautifully frame the intuitive linear calendar display. Now, this beauty of a watch is a kind of a paradox: it is an ultra-complicated timepiece bearing a few great complications — tourbillon, perpetual calendar and equation of time — yet it is just as easy to use and adjust as a three-handed watch. It should not come as a surprise that this watch earned the “best calendar” prize in the 2017 Grand Prix of Watchmaking.

Technical Specifications

Movement

Hand-wound mechanical, caliber developed by Greubel Forsey with two proprietary inventions and three patents; hours and minutes; perpetual calendar; 24H/day and night indicator; equation of time and season and year displays; 25-second tourbillon; 21,600 A/h; 72-hour chronometric-grade power reserve

Case

Red gold 5N, 43.5 mm in diameter, transparent sapphire caseback, water resistance of 30 meters

Strap

Hand-stitched, alligator leather with red gold folding clasp

Price

CHF 670,000

Greubel Forsey QP à Équation