Stupid Pope

Years which are evenly divisible by 100 are not leap years, unless they are also evenly divisible by 400, in which case they are leap years
For example, 1600 and 2000 were leap years, but 1700, 1800 and 1900 were not. Going forward, 2100, 2200, 2300, 2500, 2600, 2700, 2900, and 3000 will not be leap years, but 2400 and 2800 will be.