If you only have a Calendar or Annual watch, you probably look enviously upon those who own a Perpetual Calendar watch. Well, an opportunity is coming (not too soon!) to wipe the smug look from their faces.
Because it takes the earth 365 days, 5 hours, 48 minutes, and 45 seconds to circle once around the Sun and yet there are only 365 days in a year, we need to have leap years with a whole extra day in February. The clever Perpetual Calendar watch knows this and adjusts accordingly, every four years – brilliant!
However, the criteria for a leap year (the year can be evenly divided by 4; if the year can be evenly divided by 100, it is NOT a leap year, unless the year is also evenly divisible by 400. Then it is a leap year) means that 2100, 2200, 2300 and 2500 are not leap years.
So, on March 1st 2100 and so on, all the Perpetual Calendar watches are going to need adjusting.
In the interests of gloating, we have reproduced the instructions for adjusting your Perpetual Calendar watch from Audemars Piguet: Good Luck!