Q: What is a leap year?

A: A leap year consists of 366 days, as opposed to a regular year, which has 365 days. During leap years, the extra day is added in February, creating a Feb. 29.

Q: How often does a leap year occur?

A: A leap year occurs about every four years.

Q: What are the criteria used to determine when a leap year is happening?

A: In our modern Gregorian calendar, some criteria must be met for a year to be a leap year:

• The year must be evenly divisible by four.

• The year cannot be evenly divided by 100 unless the year is also evenly divisible by 400. Then it is a leap year.

Q: Why do we need leap years?

A: Leap years are necessary tools to keep our calendar in alignment with the Earth’s revolutions around the sun. It takes the Earth approximately 365.242199 days to circle once around the sun. So if we didn’t add an extra day, Feb. 29, about every four years, we would lose approximately six hours off our calendar every year.

Q: When were leap years invented?

A: One account is that Julius Caesar introduced leap years in the Roman Empire more than 2,000 years ago. Back then, however, the year only had to be divisible by four to be a leap year. This led to there being many more leap years than were necessary. The situation didn’t get corrected until the introduction of the Gregorian calendar more than 1,500 years later.

Find more information about leap years at timeanddate.com/ date/leapyear.html.