Question: is 200 ad a leap year?
Answer: The years 1600, 2000 and 2400 are leap years, while 1700, 1800, 1900, 2100, 2200 and 2300 are not leap years. By this rule, the average number of days per year is 365 + ​1⁄4 − ​1⁄100 + ​1⁄400 = 365.2425.