In 2017 Greubel Forsey received the best Calendar Watch Prize at the Grand Prix d’Horlogerie de Genève for the Quantième Perpétuel à Équation. Now the brand presents its QP à Équation in a 5N red gold millesime with a chocolate coloured gold dial.
The Quantième Perpétuel à Équation (Perpetual Calendar with Equation of Time) is a characteristic GF timepiece, which combines a perpetual calendar – one of the most complicated functions – with elegant simplicity.
The display of the calendar occupies one quarter of the dial and is emphasised by its nickel-silver rounded border as well as its elevated height. It consists of three apertures aligned next to each other horizontally, allowing an immediate and natural reading of the date: day of the week, date and month and a small leap year indicator at 6 o’clock.
Setting the date is also made simple as you can easily modify the date forward or backward by turning the crown clockwise or anticlockwise. (The watch has a crown pusher function selector at 3 o’clock – in H/M standing you can adjust the hours and minutes and in QP the perpetual calendar.)
At the heart of the QP à Équation lies one of the GF inventions, the Mechanical Computer – an integrated 25-part component that brings a totally new interpretation to some of the calendar functions incorporated in astronomical clocks.
On the case-back you can find the Equation of Time indication, connected to the perpetual calendar.
Since the orbit of the Earth is an ellipse, which is not centred on the Sun, and its speed also varies on this journey, the fictitious “mean” time we measure differs from the solar time which tracks the exact motion of the Sun. Sometimes the Sun, and therefore the solar time is ahead, and sometimes it’s behind the mean time – the difference can be as much as 16 minutes and 33 seconds. Equation of time describes the discrepancy between these times.
Greubel Forsey installed two superimposed synthetic sapphire disks on the back of the piece. The one driven by the date wheel has the scale of the time discrepancy, the second making one revolution a year holds a curve with four sectors. When the red sectors intersect the scale, the solar time is ahead to the mean time by the value shown on the scale. When the blue intersect, it is running behind.
The latest version of the timepiece features a multi-level chocolate-coloured gold dial, 5N red gold case and chocolate brown alligator strap.
Photo credits: Greubel Forsey
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