Have you ever thought that why do we have a Leap Year after every 4 years?. The Leap year is a trick that we use to make up fot the lost time. Now the next question is what do I mean by "Lost Time"?

The Answer is that earth takes 365.25 days to complete one orbit around the sun and we have international calendar of 365 days. In other words, after every 1 year 0.25 day is lost. So to make up for that we have 1 Extra day after every 4 years. This solution only applies to the International Calendar.