How did leap years become a thing?

Keke's here to teach you about this event that comes along every four years.
4:01 | 02/27/20

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Transcript for How did leap years become a thing?
Saturday is a very special day, an event that happens once every four years. No, not Michael getting married. I'm talking about leap year, but did you ever wonder how leap year became a thing? Well, you're about to find out. Take a look. Reporter: It's now 2020, and you know what that means. It's time to deal with that weird process we're forced to undergo every four years whether we like it or not. I'm not talking about the presidential election. I'm talking about leap year. The year that black history month becomes almost as long as the regular months. All right. All of this of course, begs the question. How did leap year become a thing? Humans had attempted to align calendars since the beginning of time, but just couldn't figure out how to get it right. Kind of like programming the clock on the VCR. Did I just make a VCR reference? How long was this written? Seven leap years ago? To understand how a solution came to be, I.e., the insertion of a leap year, we need to go back in time. Whoa. Too far back. Nope. Still too far. There we go. Okay. So 5,000 years ago, the sumerians divided 12 months with 30 days each. Totaling 360 days, classic babylonian move, am I right? The Egyptians adopted the calendar, but determined that the math didn't quite add up. The seasons were still not lined the way they should be, which may explain the old Egyptian saying, April showers bring may snowstorms. To solve the problem, it's decided that Egypt will keep the 12-month format, but add five extra days at the end of the year for festivals and parties to perfect moves like this. Oh yeah. Oh yeah. By the third century, the Egyptians were using a 365-day calendar with an additional single day every four years. Problem solved. Way to go, pharaohs. You figured out leap year. Your girl, keke is hollering at you from the future, but the Romans realized one big problem remained. The seasons were still not aligned. Enter Julius Caesar, the man behind my favorite salad. He fixed the issue by making the year 26 B.C. 445 days long in order to put the seasons back all once, randomly adding 80 days into a year? Now that's power. I can't even get my sister to return my texts. After 45 B.C., Caesar instructed everyone to follow 365 per year plus the one every four years system, and Caesar ruled happily ever after, until he was murdered two years later. History. The system was still flawed. The math didn't add up, and the calendar was 11 minutes shorter than the solar year which would come out to an additional day every 128 years. This small discrepancy resulted in major Christian holidays being shifted by about ten days. This made pope Gregor XII, if my opinion, one of the best popes to ever serve, very unhappy, which led to an adoption of the gregorian calendar. A calendar named after you. Pretty baller move, pope Gregory. The one thing is that it skipped a leap day every year with a number divisible by a hundred with the exception of numbers being divisible by 400. So the year 2000 had a leap year, but the year 2100 won't. There you have it. Thanks to the sumerians, the pharaohs, the salad guy, and pope Gregory XIII, we have the perfect movement of the Earth around the sun. Now we have to solve that unnecessary and confusing daylight saving time. Then time will all make sense. That's how leap year became a

This transcript has been automatically generated and may not be 100% accurate.

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