Catching Lost Time: The History of Leap Year

In 2020, we will experience another leap year, meaning the month of February will have 29 days instead of its usual 28. While we are all for having one extra day in our pockets, the team at Beyond were curious about the history of Leap Year came from. After a bit of research (thank you internet), we came across the answer. We also learned some surprising facts about this phenomenon of time. 

One year = 365 days, sort of.

Most of us remember learning that there are 365 days in a year. As it turns out, that isn’t exactly accurate. In truth, one solar year for the earth is approximately 365.2422 days long, or about 365 ¼ days. So the basic theory is that since four “quarters” equal a whole, every four years we make up the lost time from previous earth orbits with a single extra day. 

“Friends, Romans…lend me your years.”

Julius Caesar is considered by experts to be the “father” of the leap year. In previous centuries, many cultures relied upon lunar calendars, or they simply divided the year into 12 months of 30 days each. Both calendars fell short in matching the Earth’s actual orbit. 

For the Romans, the problem was more basic. With their old calendar, seasonal festivals were occurring out of step with the actual seasons. So as a way to ensure these festivals were held at the same time every year, Julius Caesar decided in 46 B.C. to change time in two ways: First, he instituted a 455-day “Year of Confusion” as a catchup period. Second, he established a new calendar. 

With his new calendar, Julius Caesar added days to different months of the year to create 365 days, then added an extra one at the end of February. This calendar system was reformed further by the Georgian Calendar in 1582, the one we still use today. The Georgian Calendar still retained an extra day every four years. 

Leap year does not fix the problem of time.

“So having an extra day every four years fixes things – right?” Not exactly. As it turns out, when you add an extra day every four years, you eventually add in too much. So as a result, every 100 years, a leap day is not added. As if that wasn’t complicated enough, every 400 years the leap day is added back in. Still confused? Maybe this video from Neil Degrasse Tyson will help. (Spoiler alert – it didn’t for us.)

Interested in learning more about Leap Year?

While researching the history of Leap Year, we found these additional resources. Hopefully you will enjoy them too:

National Geographic

Updated 1/17/2024