This festival of foolishness has an obscure origin. Since the new year used to be counted from the end of March, some scholars think that the day came when the Gregorian calendar was adopted in 1582, which changed New Year’s Day to January 1. Some people, though, were too ignorant to know about the switch, so they celebrated New Year’s on the wrong day, April 1, to the ridicule of those in the know who made fun of the April Fools. That’s a good story, but the day seems to have been celebrated before that! See this for background.
Nor is the post about Al Gore an April Fool’s joke, though it would make a good one. (Our problem today is that REALITY is often so close to jokery, that it’s difficult to tell them apart!)