The current record for the most accurate perpetual calendar over time is 400 years and the most accurate moon phase indicator over time has a deviation of one day in 2,060,757 years (that’s the Andreas Stehler Sauterelle à Lune Perpetuelle 2M, in case you are curious).
But now…drum roll, please…IWC has come up with a perpetual calendar that will keep perfect track of time until the year 3,999 (and it only stops there because no one has decided what to do with leap years post this date). Add to this a moon phase that will keep perfect track of the lunar cycles for 45 million years, and the lovely people from the Guinness Book of Records better get themselves over to Watches and Wonders pronto!
The Madness of the Leap Year System
Leap years were introduced to solve the problem of the Gregorian calendar being slightly shorter than a solar year by 5 hours, 48 minutes, and 56 seconds per year. It doesn’t sound much, but if we stopped using leap years, then in 700 years, summer in the Northern Hemisphere would begin in December instead of June.
To rectify this discrepancy, a leap year is added on the 29th of February every four years. But that still isn’t enough for the numbers to tally up. So, every centenary year – except for those divisible by 400, such as the years 1600, 2000, and 2400 – we skip the leap year. This is all well and good unless you are a watchmaker seeking ultimate horological perfection.
IWC’s Eternal Perpetual Calendar
For the last four decades, IWC has been perfecting the mechanical perpetual calendar, making it as efficient and easy-to-use as possible, and yet the centenary leap years were foxing them as much as everyone else in the watch industry. A renewed desire to solve the problem once and for all took them back to the drawing board, where they finally found a solution with the addition of a 400-year wheel. As the name suggests, this wheel makes one rotation every 400 years and is fitted with three little indentations to skip the centenary “non-leap” leap years, keeping the Eternal Perpetual Calendar on track for eternity, or at least until our calendar system changes.
45 Million Years of Moon Phases
In addition to the Eternal Perpetual Calendar complication, IWC has also been working on improving the precision of the moon phase (its current best performer is the Portugieser Perpetual Calendar with a moon phase accuracy of 575.5 years). But now the Schaffhausen-based brand has smashed that number to smithereens with a new record of 45 million years.
How They Did It
The time it takes to go from one new moon to the next is 29 days, 12 hours, 44 minutes, and 2.88 seconds so the duration of one calendar month must therefore be reduced as close as possible to one lunar cycle. This is achieved by placing a reduction gear between the base movement and the moon phase disc. The key for high precision lies in the quantity of wheels used, their proportions, and the number of teeth used. For this new world record, IWC’s engineers have used a special computer programme to simulate over 22 trillion different combinations that have allowed them to come up with a new reduction gear train with three intermediate wheels that will result in the moon phase indication only deviating by one day in 45 million years.
The perpetual calendar and moon phase technology in this watch is insanely cool and its design has been created to match that with a 44.4mm platinum case, glass dial featuring white lacquer and a black alligator leather strap. You can find more details here.
Now all we have to do is figure out how to live that long!
