Question: are the leap years since 2000?
Answer: So 2000 and 2400 are leap years but 1800, 1900, 2100, 2200 and 2300 are not. Apart from that, every year divisible by 4 (2012, 2016, 2020, 2024, etc.) is a leap year. Example: look just before 2100, the worst year is 1.2 days ahead, but because 2100 is not a leap year they all get adjusted back by 1 day.