Believe it or not, most people like to be fooled every now and then; thus, it's no great surprise we have an entire day devoted for just this purpose - April Fool's Day.

Although historians have put out numerous explanations for the origin of this day, the most plausible is the one that follows.

In France, April 1st was, for a time, New Year's Day. In 1582, though, Pope Gregory declared that he would change the calendar from the older, Julian, calendar, to the newer, Gregorian, one. With this change, New Year's Day was officially changed to January 1st.

Unfortunately, however, it took quite some time for every person in France to hear about this change, and of those who did, numerous ones obstinately refused to accept the new calendar. That meant a lot of people still celebrated New Year's Day on the first of April  earning them the name April fools.

The April fools were subjected to ridicule and practical jokes, and the tradition of mischief-making was born. The butts of these pranks were first called "poisson d'avril," or April fish, because a young, naive fish is easily caught. A common practice was to hook a paper fish on another person's back. The fish evolved over time, but the continued custom of prank-playing still continues on the first day of April around the globe.