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Monday, February 29, 2016

The Origin of Leap Years

This year, being divisible by four, is a leap year. As all of you probably know, a leap year is when an extra day is added to the end of February (meaning an extra day of school this year...yay?). But how did this (fairly strange) practice originate?

First, some background. Leap years are needed because the orbital period of the Earth is 365.2421 days, not a perfect 365. In order to account for the extra time, every fourth year has 366 days. This prevents the Earth's movement from becoming off-sync with the calendar over time.

The first people to notice the need for a leap year were the ancient Egyptians. Europeans began using leap years during the rule of Julius Caesar. During his reign, an inconsistent lunar calendar was replaced with the "Julian calendar" based off of the sun.

But simply adding leap years is not enough to fix the calendar. Leap years assume that an orbit is 365.25 days, which adds a few extra minutes per year. In order to counteract that, every year divisible by 100 but not 400 is not a leap year. (So 1700 was not a leap year, but 1600 was). This change was first made by Pope Gregory XIII in the modern "Gregorian" calendar.

I hope you found that interesting! Feel free to share any special leap day plans in the comments.

Written by Jenna M., Homework Assistant


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