Why the April Fool’s Joke? There Are Lots of Theories @librarycongress

Stephen Winick writes about the origins of the April Fools joke, here, for Folklife Today. He says in part, 

But where do we get the strange custom of playing pranks on April 1? The short answer is that nobody knows for sure. All we know is that the custom was known in Renaissance Europe, and probably has roots older than that.

Some people think the idea of April Fools’ Day goes back to classical Roman times, when a joyful festival called Hilaria, originally probably an equinox celebration, came to be celebrated on March 25. In Roman terms, March 25 was called “the eighth of the Calends of April,” which associates the festival strongly with April 1, the Calends of April. However, there’s no hard evidence to connect Hilaria with April Fools’ Day, so this is just one of many guesses advanced by curious people.