Why all the embarrassment on a day that should be beautiful, warm and full of early spring?
Blame it on the calendar. Museum of Hoaxes explains:
The most popular theory about the origin of April Fool’s Day involves the French calendar reform of the sixteenth century.
The theory goes like this: In 1564 France reformed its calendar, moving the start of the year from the end of March to January 1. Those who failed to keep up with the change, who stubbornly clung to the old calendar system and continued to celebrate the New Year during the week that fell between March 25th and April 1st, had jokes played on them. Pranksters would surreptitiously stick paper fish to their backs. The victims of this prank were thus called Poisson d’Avril, or April Fish—which, to this day, remains the French term for April Fools—and so the tradition was born.
The calendar-change hypothesis seems, on the surface, like a logical explanation for the origin of April Fools. However, the hypothesis becomes less plausible if we examine the history of calendar reform in more detail.
The article goes on to counter the above theory and is actually pretty interesting if you, like me, love history. I see all the holes in calendar theories, but it is pretty coincidental that April 1 was the previous start of the year. This explanation makes perfect sense to me! Then again, I am admittedly gullible...
For a great list of April Fool's Pranks (as well as further origin speculation), see Wikipedia here.
Left Handed Whoppers: In 1998, Burger King ran an ad in USA Today, saying that people could get a Whopper for left-handed people whose condiments were designed to drip out of the right side. Not only did customers order the new burgers, but some specifically requested the "old", right-handed burger.