A leap year has 366 days, adding February 29. A year is a leap year if it is divisible by 4 — except century years, which must be divisible by 400 (so 2000 was a leap year but 1900 and 2100 are not). Here are the leap years from 2000 to 2100.
2000, 2004, 2008, 2012, 2016, 2020, 2024, 2028, 2032, 2036, 2040, 2044, 2048, 2052, 2056, 2060, 2064, 2068, 2072, 2076, 2080, 2084, 2088, 2092, 2096