The science of astronomical watches, an age-old tradition at Vacheron Constantin
- 1884: Vacheron Constantin presents its first pocket watch with a perpetual calendar known to date.
- For more than a century, this mastery of astronomical indications has been confirmed in the Maison’s grand complication calibres.
- The Vacheron Constantin collections perpetuate this tradition in which technical sophistication vies with aesthetic elegance.
Geneva, May 13th 2019 – The vagaries of the Gregorian calendar have enabled watchmakers to exercise their genius in devising mechanical representations of these quirks. At Vacheron Constantin, this resolutely horological approach to astronomy was strongly expressed as early as the 19th century. Greatly appreciated by shrewd connoisseurs, it continues today in the Maison’s collections.
The perpetual calendar is one of the horological complications regarded by connoisseurs as masterpieces of mechanical engineering. This is due to their level of complexity, as well as because these calendar displays are a direct consequence of astronomical observations made since the first civilisations. For those who grasp its full depth, a watch with a perpetual calendar very quickly becomes a link with the cosmos – and one that is all the more symbolic in that it requires consummate watchmaking science to create.
The perpetual calendar is a mechanical solution to an astronomical problem. From ancient Egypt to Rome and Greece, and from astronomers to mathematicians and priests, the history of the calendar has mainly revolved around the question of fitting the lunar and solar calendars within a system of integers (whole numbers).
The Gregorian calendar
In 1582, Pope Gregory XIII reformed the Julian calendar used in Europe since its introduction by Julius Caesar in 46 BC and instated the Gregorian tropical solar calendar. Subsequently adopted over the centuries by the international community, it is currently the most widely used civil calendar. The reason for the reform was that the Julian calendar was drifting, so that the Easter feast day, linked to the spring equinox, was no longer in step with its ritual season.
The Julian calendar had 365 days, whereas the solar year or "tropical year” – meaning the time required for a complete revolution of the Earth around the Sun – lasts exactly 365 days, 5 hours, 48 minutes, 45 seconds, or 365.2421875 days. The Gregorian calendar compensates for this difference by adding a 29th day to February every four years. It provides a system that indicates the seasons accurately and runs from January 1st to December 31st in 365 days and 12 months. However, given its solar nature, its dates do not indicate moon phases.
The 12 months of the Gregorian calendar consist of 28, 30 and 31 days. Each year divisible by four is a leap year, apart for those divisible by 100, although there is an even exception to this exception: century years exactly divisible by 400 are nonetheless leap years. For example, the years 1700, 1800 and 1900 were not leap years, whereas the year 2000 was.
The only thing that owners of a perpetual calendar watch and their descendants will need to do is to adjust it at each turn of the century, unless the given century is divisible by 400.
A late 18th century horological complication
For a long time, such peculiarities proved a problem for watchmakers seeking mechanisms capable of reproducing them without human intervention. The solution finally came from the invention of a component called a "cam", a kind of mechanical memory generally based on a 48-month cycle. This disc has notches of different depths, each of which indicates a certain type of month with either 30 or 31 days. The February satellite, which is on two levels, indicates months of 28 and 29 days. The deeper the groove, the shorter the month. The information provided by the cam is passed on via a feeler-spindle to a large yoke that activates the various displays.
The perpetual calendar is complex to adjust because it must be set according to a four-year cycle, and four years must pass to ensure that it works perfectly – even if the four-year cycle is simulated on a machine.
The archives of Vacheron Constantin reveal a first perpetual calendar in 1884, integrated into a double-sided yellow gold pocket watch, now part of the Maison’s private collection. This was the beginning of a mechanical "epic" that would singularly take shape at the turn of the century. In 1900, the Maison set up a workshop exclusively dedicated to the assembly of watches with complications. And orders did indeed flow in for complicated, even very complicated watches. The perpetual calendar was then combined with other technical feats such as in this 1905 pocket watch featuring a minute repeater, split-seconds chronograph and perpetual calendar with phases and age of the moon.
A late 18th century horological complication
For a long time, such peculiarities proved a problem for watchmakers seeking mechanisms capable of reproducing them without human intervention. The solution finally came from the invention of a component called a "cam", a kind of mechanical memory generally based on a 48-month cycle. This disc has notches of different depths, each of which indicates a certain type of month with either 30 or 31 days. The February satellite, which is on two levels, indicates months of 28 and 29 days. The deeper the groove, the shorter the month. The information provided by the cam is passed on via a feeler-spindle to a large yoke that activates the various displays.
The perpetual calendar is complex to adjust because it must be set according to a four-year cycle, and four years must pass to ensure that it works perfectly – even if the four-year cycle is simulated on a machine.
The archives of Vacheron Constantin reveal a first perpetual calendar in 1884, integrated into a double-sided yellow gold pocket watch, now part of the Maison’s private collection. This was the beginning of a mechanical "epic" that would singularly take shape at the turn of the century. In 1900, the Maison set up a workshop exclusively dedicated to the assembly of watches with complications. And orders did indeed flow in for complicated, even very complicated watches. The perpetual calendar was then combined with other technical feats such as in this 1905 pocket watch featuring a minute repeater, split-seconds chronograph and perpetual calendar with phases and age of the moon.
More recently, in 2015, Reference 57260 and its 57 complications, a specially commissioned one-of-a-kind model, laid a new milestone in watchmaking history. This was followed two years later by the Cabinotiers Celestia Astronomical Grande Complication 3600 watch, which once again pushed the limits of feasibility with its combined display of civil, solar and sidereal time. All this was naturally complemented by a perpetual calendar with moon phases, a common denominator in the watchmaking world according to Vacheron Constantin.
In 2019, the Traditional Twin Beat perpetual calendar features an innovative mode of operation with two gear trains running at different rhythms: in moving from a first high-frequency oscillator (5Hz or 36,000 vph) – synonymous with ultimate precision – to the second rate of 1.2Hz (8,640 vph), the watch switches to ‘resting’ mode, thereby serving to extend the power reserve to at least 65 days. The accuracy of the calendar indications thus remains intact for more than two months, avoiding any improper handling of the calendar mechanism. Finally, in a style that is both timeless and contemporary, the new Patrimony ultra-thin perpetual calendar adds its discreet elegance to the technical prowess of the 1120 QP calibre, by displaying moon phases and perpetual calendar on a sunburst midnight blue dial.
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TECHNICAL DATA
Patrimony perpetual calendar ultra-thin
Reference 43175/000R-B519
Calibre 1120 QP
Developed and manufactured by Vacheron Constantin
Mechanical, self-winding
29.6 mm (12½’’’) diameter, 4.05 mm thick
Approximately 40 hours of power reserve
2.75 Hz (19,800 vibrations/hour)
276 components
36 jewels
Hallmark of Geneva certified timepiece
Indications
Hours, minutes
Perpetual calendar (day of the week, date, 48-month display with leap year indication)
Moon phase
Case
18K 5N pink gold
41 mm diameter, 8.9 mm thick
Transparent sapphire crystal caseback
Water-resistance tested at a pressure of 3 bar (approx. 30 meters)
Dial
Midnight blue with sunburst satin-finishing
Convex external zone with circular “pearl” minute-track
18K 5N pink gold applied hour-markers
Strap
Dark blue Mississippiensis alligator leather with alligator inner shell, tone-to-tone stitching, saddle-finish, large square scales
Clasp
18K 5N pink gold folding clasp
Polished half Maltese cross-shaped
Available exclusively from Vacheron Constantin boutiques.