Gisbert L. Brunner, who was born in 1947, has worked with every sort of precision timepiece, though mainly wristwatches, since the 1960s. He has now published more than 15 books on the subject. The author is also in demand the world over as a public speaker.
Let’s suppose you wear a wristwatch day in day out or attach it to a rotator which stretches the mainspring consistently when you’re doing outdoor activities and you don’t have to change the date, the day of the week or the month till the end of February 2100. Of course, the mechanics, subject to reappraisal every five to six years, have to play ball too. But why until 2100 specifically? It’s very simple! As we know, all years divisible by four have 366 days. In those years, as in 2016, February has 29 days. Leap years hark back to Ancient Egypt.
Gaius Julius Caesar probably brought them back with him from his military campaigns and used them in the Julian calendar named after him. But he and his astronomer Sosigenes had worked out the year to be 0.0078 days longer than it actually was, so Pope Gregory XIII improved things in 1582. As per his Gregorian calendar, there is no February 29 in secular years, unless the year is divisible by 400. As per this system, 2000 was a leap year. But 2100, 2200 and 2300 won’t be.
We call calendars which take the different lengths of various months into account, whether it’s a leap year or not, perpetual calendars. The very smallest of these, which include the brand new “Slimline” model by Frédérique Constant, can even deal with these Gregorian exceptions, which explains why perpetuity only lasts until February 28 2100 and not a day longer. For then the switching mechanism, thinking it a standard leap year, will move on to February 29 at midnight whereas in fact March 1 will have already dawned over all humanity.
Yet that little shortcoming is easy to get over, especially since the Frédérique Constant CEO, Peter C. Stas, has made this wristwatch available at an extremely competitive price. Many of my esteemed readers will be astonished to see that the steel version is retailing for a mere €7,995, while the gold-plated edition goes for €8,295. And they should be no less astounded by the fact that the mechanics built into the Slimline case are all in-house. I currently know of no other European wristwatch with a perpetual calendar selling at such a reasonable price. When you take into account the manufacturing aspect too, you get an awful lot of watch for relatively little money with Frédérique Constant.
There’s method to such madness, Peter told me. His Geneva-based family business, which doesn’t publish sales figures, produced about 145,000 watches in 2015 and would like to increase that figure to 160,000 in 2016. They would like to systematically counter the trend of ever-increasing prices for watches and the difficult situation on the international watch markets with their work.
For the Slimline Perpetual Calendar, master watchmaker Pim Koeslag and his team developed a new switching device whose functions still hark back to conventional solutions. The memory, i.e. the month cam, has notches which differ in length. The notches inform the mechanics of the length of each month. Another component comes into play when February has but 28 days clear. So that the watch can easily be reset if it has gone unused for a long time, a leap-year indicator comes as standard.
Unlike the calendar, this standard moon phase indicator, which works to round months of 29 and a half days using a 59-cog pulley, is already one day out within three years. To make adjustments, there is a recessed push piece on the side of the case.
The 775 automatic calibre is also manufactured in-house. It is a new iteration of the 7xx calibre family and measures 30 millimetres across. Its central rotor stretches the mainspring in both directions. Once fully wound, there is enough energy for the balance wheel to oscillate at four Hertz for 42 hours.
I am not allowed to publish photographs before Baselworld 2016 but I can show you the official video. Here are a few screenshots taken from it. This outsized plastic model shows the calendar switching mechanism in great detail.
And for all those wondering where the technical word for the switching mechanism – cadrature – comes from, let me reveal all: the French for “dial” is cadran. So watchmakers christened the mechanisms under the dial, such as those for a perpetual calendar, “cadrature”.