When did April Fool's Day begin?

msnbc.msn.com — A giddy spurt of practical joking seems to have coincided with the coming of spring since the time of the Ancient Romans and Celts, who celebrated a festival of mischief-making. The first mentions of an All Fool's Day (as it was formerly called) came in Europe in the Middle Ages. Apr 1, 2009 View in Crawl 4