Question

How is leap year made

Answer 1

February 29 is a date that usually occurs every four years, and is called leap day. This day is added to the calendar in leap years as a corrective measure, because the Earth does not orbit the sun in precisely 365 days

The simple reason for leap year is that the earth revolves around the sun in approximately 365.25 days, and so to make sure that a calendar year is the same as a tropical year (which is the period of earth's revolution), there needs to be an extra day added every 4 years. But then, even that doesn't make the calendar accurate (the earth doesn't revolve around sun in exactly 365.25 days), so there's another rule that years which are divisible by 100 have to be also divisible by 400 for it to be a leap year.