This year 2100 is of importance for mechanical watches, because according to the
Gregorian calendar it is not a
leap year. Some
perpetual calendars (eg by
IWC) support the consideration of this exception by a single operator intervention.
Svend Andersen in
1996 reached the accievement even to automate this change, with his development of the wristwatch
Perpetual Secular Calender Namely the watch has a wheel that only rotates once every 400 years and so balances the absence of a leap year in 2100, making it the world's first wristwatch that can do that.