There is a leap year every four years. However, there length of the Earth's orbit is not exactly 365. 25 days; it is actually a little longer. So, every century we need a few additional days. read more
Any 200-year period has either 48 or 49 leap years, depending on whether or not the period includes a year that is evenly divisible by 400 (any 400-year period always has 97 leap years). read more
Leap years occur once in 4 years. So, there are 200 : 4 = 50. But, sometimes one will be missed because divisible by 100 but not by 400, so you will get only 49. read more