There is a leap day every 4 years because Earth finishes one cycle around the sun in around 365 days and 6 hours. Over a time of 4 years, the additional 6 hours from every year get combined up to become a complete day (6*4=24 hours). Hence, we possess a leap day/leap year every 4 years.
The period of February is a wee bit distinctive from other months in the sense that every 4 years, out of nowhere, a 29th day is affixed to it, and the month of February grows one day longer than usual!
What is a leap year?
A leap year comprised of 366 days as objected to a ‘regular’ year that consists of 365 days. Every 4 years, a year happens along that has one more day to it, meaning 366 days in total. Those years with 366 days are leap years. More precisely, the year in which the moon of February has 29 days (instead of the usual 28 days) is deemed a leap year. For example, the year 2016 was a leap year.
How often is a leap year?
A leap year arrives every 4 years. A regular year has 365 days, but every 4 years, a leap year begins which has 366 days, i.e. 1 day more than a normal year. 2020 is a next leap year.