Historians aren't pulling your leg when they say no one is quite sure about the origins of April Fools' Day. 

April 1, the annual day of shenanigans, pranks, tricks and hoaxes, falls on Monday this year. While historians are unsure of the exact source of the tradition, they do know the custom goes back centuries, at least back to Renaissance Europe and possibly back to Roman times. Here's a look at what the experts say.

Theories, both real and false, tie April Fools' Day to Roman times 

Some believe April Fools' Day dates back to Hilaria festivals celebrated during classical Roman times. The festival was held on March 25 which, in Roman terms, was called the "eighth of the Calends of April," according to the Library of Congress. 

One theory tying the source of April Fools' Day to Roman times is a hoax. In 1983, an Associated Press reporter reached out to Joseph Boskin, a historian at Boston University, to discuss the origins of April Fools' Day. Boskin spun a tall tale to the reporter, assuming it would be fact-checked and revealed as fake. 

It wasn't. 

According to the story Boskin made up, a group of jesters convinced Emperor Constantine to make one of them king for a day. The appointed jester, named Kugel, declared it would be a day of levity. 

"I got an immediate phone call from an editor there, who was furious, saying that I had ruined the career of a young reporter," Boskin said in a Boston University post. "He said I told a lie. 'A lie?' I asked, 'I was telling an April Fools' Day story.'"

Middle Ages 

Some historians believe France is responsible for the humorous tradition, tying it to a calendar change in 1582, according to the History Channel. That year, France implemented the Gregorian calendar, shifting the start of the New Year from the spring equinox, which usually falls around April 1, to January 1. 

After the change, people who wrongly celebrated the new year in late March and early April were called "April fools."

The first clear reference to April Fools' Day is a 1561 Flemish poem by Eduard De Dene, which tells the story of a servant being sent on "fool's errands" because it's April 1, according to the Library of Congress. 

What are some famous April Fools' Day pranks?

In 1957, the BBC ran a broadcast on the Italian spaghetti harvest that pretended the pasta was being harvested from trees. 

The BBC also ran an April Fools' report on flying penguins in 2008.

In Los Angeles, airline passengers were greeted with a banner saying "Welcome to Chicago" after landing on April 1, 1992, CBS Sunday Morning previously reported.

Taco Bell in 1996 advertised that it had bought the Liberty Bell and renamed it the "Taco Liberty Bell," according to the company.

As part of a 1997 April Fools' Day joke, Alex Trebek, host of "Jeopardy," swapped places with "Wheel of Fortune" host Pat Sajak, according to jeopardy.com.

On April 1, 2015, streaming giant Netflix shared faux public service announcements to remind viewers to "Binge Responsibly."

In:
• April Fools' Day

Aliza Chasan

Aliza Chasan is a digital producer at 60 Minutes and CBSNews.com. She has previously written for outlets including PIX11 News, The New York Daily News, Inside Edition and DNAinfo. Aliza covers trending news, often focusing on crime and politics.

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