1. It may have been a French calendar error. Historians think that April Fools' Day was created due to a calendar error made by France, when in 1582, the country switched from the Julian calendar to the Gregorian calendar. This caused the celebration of New Year's Day to move from April 1 back to January 1. And anyone who continued to celebrate the arrival of the new year at the beginning of April was labeled a fool.
2. England made it cool. While the origins of the holiday are still somewhat unknown, it IS known that England made April Fools' Day happen (unlike Gretchen Wiener's case for "fetch") in 1700, as a day for people to play pranks on each other. The tradition quickly gained popularity throughout the U.K. during the 18th century.
3. In Scotland, it's all about the booty. The Scots made April Fools' Day a two-day celebration, and the second day is called Tailie Day, when pranks involving people's butts are encouraged (enter "kick me" signs).
4. Some pranks truly fooled the masses. In 1957, BBC ran a story that farmers in Switzerland were having a record year with their spaghetti crops, and that noodles were growing on trees. In 1996, Taco Bell released a full-page ad in several newspapers stating that it had purchased the Liberty Bell in Philly and was renaming it "The Taco Liberty Bell." And in 1998, Burger King announced that it would be releasing a new burger called the "Left-Handed Whopper" specifically designed for all those poor lefties who had previously been unable to fully enjoy the classic.
5. Some pranks are still going strong. One classic prank has turned into a beloved tradition. Since 1986, a press release is created each year to promote the annual New York City April Fools' Day parade. There is no parade, but we're going on the 31st year of this nonexistent event.
6. You really can't trust anything on April 1. Every year, the pranks get more and more creative, leaving the population in a paranoid state at the start of April. So beware of engagement and pregnancy announcements on social media. Be wary of seemingly outlandish breaking news stories.