How did April Fools Day Start?

It's started in the year 1500,when the gregorian calendar took over from the Julian.Those who forgot the change and attempted celebrate New Year's ( previously celebrated on the 1st of April) on the wrong date were teased as April Fool's.
April Fools' Day, sometimes called All Fools' Day, is one of the most light-hearted days of the year. Its origins are uncertain. Some see it as a celebration related to the turn of the seasons, while others believe it stems from the adoption of a new calendar.