Tomorrow is April Fools Day. It's one of the most light-hearted days of the year. Origins of April Fools Day are obscure. The most commonly cited theory holds that it dates from 1582, the year France adopted the Gregorian Calendar, which shifted the observance of New Year's Day from the end of March (around the time of the vernal equinox) to the first of January. You might search for some original April Fools Day prank in the past. Here are some of the April Fools Day pranks.