MAY YOU HAVE FUN PLAYING TRICKS TODAY!
Here is a vintage post card from my collection. The text has faded... you can barely make out 1st April at the top.
There's some uncertainty about when and where this bizarre tradition began, but the most accepted explanation traces April Fools' Day back to 16th century France. Up until 1564, the accepted calendar was the Julian calendar, which observed the beginning of the New Year around April. According to "The Oxford Companion to the Year," King Charles IX then declared that France would begin using the Gregorian calendar, which shifted New Year's Day to January 1.
....Today in France, people who are fooled on April 1 are called Poisson d'Avril, which literally means the "April Fish." One common joke is to hook a cardboard fish to the back of a person. What a fish has to do with April Fools' Day is not clear.
Above from How Stuff Works... read more HERE!