Did you know that a perpetual calendar isn’t perfect? That’s why the description for a perpetual calendar says that it will correctly show the date until the year 2100 – it doesn’t say that it will always correctly show the date. Why is this, you ask?
Let’s take a step back. How long is a year? The number commonly used is 365.25 days. The decimal 0.25 is, of course, equal to the fraction 1/4. So that means you need to add an extra day every four years…which we accomplish by adding a “leap day” once every 4 years. All good, right?
Well, not quite. It turns out that a more accurate number for the length of a year is 365.2425 days. The decimal 0.2425 is equal to the fraction 97/400 That means we only need to add 97 extra days every 400 years, not 100 extra days as the previous 1/4 fraction gave us. So where did those missing 3 leap days go? The Gregorian Calendar that we use every day actually takes this into account by saying a leap year occurs every 4 years, unless the year is evenly divisible by 100, but not evenly divisible by 400. So that means 2016 is a leap year, as is 2020, 2024, … all the way up to 2096. But 2100 is not a leap year, because it is evenly divisible by 100 (2100/100 = 21), but not evenly divisible by 400 (2100/400 = 5.25); similarly, 2200 isn’t a leap year either, but 2400 is a leap year since it is evenly divisible by both 100 and 400 (as was the year 2000).
Back to watches – a perpetual calendar watch cannot handle this exception in the year 2100, 2200, etc., but a secular perpetual calendar can!
As far as we know, only two secular perpetual calendar wristwatches have been made – the Mega Aeternitas 4 by Franck Muller and this Perpetuel Secular Calender by Andersen Genève. By the way, the Aeternitas is an ultra-complicated watch with a price tag well north of $2 Million.
We spoke with Svend Andersen at Baselworld 2016, and he said that he’s actually only made about 12 to 15 of these watches in his career! (The serial number of #37 on this watch might be a little misleading, but it’s because he numbered his calendar watches together. Therefore, most of the watches in this series of serial numbers are not secular perpetual calendar watches).
In addition to being rare and interesting, this watch is also a visually treat. That central guilloché is beautiful, and those lugs are sharp and crisp. And a rear dial is always a delight–especially one that conveys the information so simply and clearly!
This is a full box and papers set. Did we mention that the original box for this watch is a Scatola del Tempo winding box? Just another indication of how special this piece is.
Andersen Genève Perpetuel Secular Calender
Case: White gold, 41mm
Movement: Modified ETA 2892
Dial: Silver dial with blued hands and hour markers
Condition: Watch is in very good condition
Includes: Box, certificate, and manual. See photos for more details.
Early in his career, Andersen received some great publicity by creating a clock in a bottle. This was published in Popular Mechanics magazine in 1970 and earned Andersen the nickname “Watchmaker of the Impossible”. It also landed him a job at the complications department at Patek Philippe.
The De Bethune DBS
The DBS was the first watch by De Bethune to have their now signature 3D moonphase complication. They make it by taking a half sphere of steel and a half sphere of palladium and combining them to form a full sphere. Both halves of the sphere are silvery-colored to start with, but then they apply heat. The metal properties of steel are such that it turns blue at a noticeably lower temperature than palladium, so the steel half of the sphere ends up turning blue while the palladium side is perfectly unchanged. The result is a perfect half-blue sphere. Such is the level of detail that exemplifies De Bethune. Click to take a closer look at this piece!