It takes approximately 365.25 days for Earth to orbit the Sun — a solar year. We usually round the days in a calendar year to 365. To make up for the missing partial day, we add one day to our calendar approximately every four years. ... This is called a leap year.

How is leap year calculated?

To check if a year is a leap year, divide the year by 4. If it is fully divisible by 4, it is a leap year. For example, the year 2016 is divisible 4, so it is a leap year, whereas, 2015 is not. However, Century years like 300, 700, 1900, 2000 need to be divided by 400 to check whether they are leap years or not.

Why is leap year in February?

It takes approximately 365.25 days for Earth to orbit around the Sun. We usually round the days to 365 and to balance the missing partial days, we add one day to our calendar every four years. That is a leap year.