Today is April 1st and lots of pranks are sure to be played.
The origin of the day is uncertain but it does date back to the 1500's, which maybe the time that the day originated. They changed calendars, moving New Year's to January instead of April 1. Some refused to honor the new calendar and were ultimately regarded as fools. source
One of the best April Fool's pranks (IMO) was a TV show on the BBC in 1957 about Switzerland experiencing an early spaghetti harvest. *blinks* yes a spaghetti harvest.
Enjoy the day. And don't be an April Fool.