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The History Behind Leap Year-What is it?

Once every four years, a calendar oddity occurs. Because human-made calendars generally have 365 days, Leap days are added every four years to help our calendar stay matched up with the same seasons every year. The solar, or tropical year that influences seasons is about 365.2422 days long. (A solar year is how long it takes the Earth to revolve around the sun.) Even though .2422 of a day doesn’t sound like much, ignoring that fraction means eventually our seasons won’t fall in the same months every year. If the calendar didn’t match the seasons, farmers would have a more difficult time growing crops, which could affect food supplies, kids would end up having summer in spring, and equinoxes and solstices would be changed. That’s why, in the 16th century, the Gregorian calendar—the most commonly used today—started adding leap days to match the calendar with the seasons. Because four .2422 days equals about one day, February 29th is now added to most years that are divisible by four, like 2020.

Julius Caesar, Father of Leap Year

Julius Caesar was behind the origin of leap year in 45 BCE. The early Romans had a 355-day calendar, and to keep festivals occurring around the same season each year, a 22- or 23-day month was created every second year. Julius Caesar decided to simplify things and added days to different months of the year to create the 365-day calendar; the actual calculations were made by Caesar’s astronomer, Sosigenes. Every fourth year following the 28th day of February (February 29th), one day was to be added, making every fourth year a leap year.

In 1582, Pope Gregory XIII refined the calendar with the rule that leap day would occur in any year divisible by four, as described previously. (Bellis, Mary. “The History of Leap Year.” ThoughtCo, April 5th, 2023,

Other fun facts about Leap Year:

1. February 29th is called Leap Day

2. If you are born on February 29th, you are called a leapling or a leaper

3. February 29th has traditionally been a day on which women were allowed to propose to men.

4. Some consider February 29th to be an unlucky day

5. In Italy, people say, “Anno bisesto, anno funesto,” which translates as “leap year, doom year.”

6. In some countries, like Greece, people warn against planning weddings during leap years.

7. February 29th is not a legal day. Many companies don’t recognize Leap Day as a “valid day.” They make leapers choose February 28th or March 1st as their birthday instead.

8. Lots of people work for free on February 29th. Most employees who are paid fixed monthly incomes will work for free on February 29th because their wages are likely not calculated to include the extra day.

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