Ever wonder why?
Back in the day April 1st, the first day of spring, was considered the New Year.
When the New Year day moved to January 1st, some folks kept to April 1st as the New Year’s beginning and hence they were called April Fools. Of course this all started in France! And it was the handiwork of a King. I kid you not. Here is a link to the Wikipedia page for even more info.