There’s a Bonus Day in February this Year!

By FPL_RyanC

Why do we not always have a February 29? A simple reason is the Earth’s orbit. The full calendar year was created to mimic the Earth’s orbit around the sun. However, the Earth’s orbit is not a whole number of days according to our calendar. It is about 365.2422 days for the Earth to orbit fully around the sun, according to National Geographic.

But how do we attribute for the .2422 days? This is where leap years come from. Every 4 years we get an extra day in February, to make up for the .2422 days. According to National Geographic, if we did not include this “leap day”, our seasons would change months throughout the years.  

Where exactly did “leap day” come from? The first time we see the concept of leap years is with the Egyptians and their lunar calendar based on the moon’s location. The Egyptian calendar year in the 3rd century BC corresponded with 360 days, with 3 seasons of 120 days. This would leave 5 days left over every year. To make up for these days, they added a “lunar month” every few years to account for these days.

In ancient Rome, Julius Caesar borrowed the idea from the Egyptians. He tweaked this concept of leap year to add an extra day on the Julian calendar in February every four years, like what we have now.

However, by the 16th century, certain marker days, such as Easter, were approximately 10 days off. The Julian calendar was short 1 day every 128 years. Pope Gregory XIII created the Gregorian calendar, of which we use today. This has a leap year every 4 years with an exception, this would not occur during centurial years that are not divisible by 400. This would exclude the years 1700, 1800, and 1900, but include the year 2000. There are some flaws however with this measure, every 3,030 years will fall one day short.  


Britannica: Egyptian Calendar, opens a new window

USA Today: What is a leap year?, opens a new window