what is leap year

A leap year is a calendar year that contains an additional day compared to a common year. This extra day, February 29th, is added to keep the calendar year synchronized with the astronomical year, which is slightly longer than 365 days. The Gregorian calendar, which is the most commonly used calendar today, has a set of rules to determine leap years: the year must be evenly divisible by 4, but if it can also be evenly divided by 100, it is not a leap year, unless it is also evenly divisible by 400. This is why the year 2000 was a leap year, but the years 1700, 1800, and 1900 were not. Leap years are important to ensure that our calendar matches the solar year, which is the time it takes for Earth to orbit the Sun, and to keep the seasons from drifting over time