Greubel Forsey opens new horizons with a revolutionary
interpretation of one of the oldest watchmaking complications — the Perpetual
Calendar. The inventive watchmakers in La Chaux-de-Fonds have also incorporated
the Equation of Time in a demonstration of how to add complexity of function
while simplifying with clear legibility and easy operation.
Greubel Forsey has pushed beyond the previous limits
of watchmaking, with no fewer than six major inventions, and a focus on
ground-breaking inclined tourbillons. Now it’s time to reinvent the horological
complication in the original sense of the term, and to show that in this area
as well, watchmaking is in a perpetual state of evolution. The technically and
ergonomically innovative Double Balancier 35° and GMT provided the springboard
for this new take on the time-honoured perpetual calendar.
The
Mechanical Computer
The perpetual calendar remains one of the most
representatives of horological complications and also one of the oldest. A direct descendant of the computus (Latin
for calculation) that the clergy used to determine the religious and seasonal
feasts of the seasons, these ancient mechanical perpetual calendars underpinned
rural society from the early Middle Ages. A prime example can be found in the
Strasbourg cathedral clock.
Comfort and
clarity
This reinvention of the perpetual calendar integrates
the Equation of Time into the perpetual calendar, as well as practical new
functions and indications that improve clarity. The priority was to simplify
the complete displays and make it easier to set the perpetual calendar by using
the bi-directional winding crown. Despite the complete indications and
functions, Greubel Forsey's mechanical computer with Equation of Time is as
easy to set as a simple date feature.
You do not need obscure instructions or a special tool
for multiple pushers. If your timepiece has stopped for several days and you
need to take an imminent flight, simply pull out the crown checking the
selection indicator near 2 o'clock. Turn the crown back and forth to change the
calendar and all the different indications change by themselves. If you go too
far, you just go back through the days until you get to the right date. It’s
easy, intuitive and pleasant to use.
To meet this technical challenge Greubel Forsey
developed a sophisticated coding mechanism: the mechanical computer for which
three patents were filed. A stack of cams with movable fingers shift the
indications on the front and back dials of the timepiece, the complete
mechanism fitting entirely within the movement without increasing its
dimensions. The cam for the months changes the month in a window on the front
display and also moves the Equation of Time scale on the back. The years' cam
controls the leap year indication on the front and that of the seasons on the
back. The development of this coding device not only overturns conventional
ways of setting the indications but also by displaying them simultaneously on
front and back dials.
Just a glance at the subdial at 3 o’clock clearly
reveals the three in-line windows that clearly indicate the day, the date and
the month. The large date makes the calendar extremely legible.
Equation of
Time
The equation of time merits further explanation.
Horology seeks to measure time as regularly as possible; however the Earth
orbits the Sun in an elliptical path. As the Earth sweeps close past the Sun,
the period between successive solar zeniths, or the solar day’s length,
changes. This causes the difference between solar time and mean time to vary
from a few seconds to as much as 16 minutes during the year. The Equation of
Time is the conversion factor between solar and mean time. To read solar time,
look at the back subdial for the displayed date’s Equation of Time.
In the spirit of the GMT, Greubel Forsey continues to
put time to better service; where the back of the timepiece is not just there
to showcase for fine hand finishing, but also provides a new way to tell the
time. The most frequently sought calendar information, namely the day, date and
month, is displayed in a line on the front dial. Information that is less often
required is on the back of the timepiece.
Thus the two sides show indications that you need to know regularly on
the front, and indications accessed less frequently on the back.
On the back of the QP à ÉQUATION you find the Equation of Time indication, the seasons
and the current year in four figures.
The indications on the back are made up of two
superimposed transparent discs in synthetic sapphire crystal. The first disc is
driven by the date wheel and has a scale in minutes indicating the difference
between solar and mean time.
The second disc, which goes around once a year, has a
figure shaped like a manta ray, and divided into four sections in red and blue
to show whether the Equation of Time is positive or negative. To find out, look
where the red line (positive difference) or the blue line (negative difference)
crosses the scale. This Equation of Time display is unprecedented and provides
a clearer appreciation of the Earth’s elliptical orbit around the sun as well
as the equinoxes and solstices
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