April Fool’s Day
The history of April Fool's Day is not totally clear, unlike most of the other non-foolish holidays. It originated in France in 1562 when Pope Gregory replaced the Julian calender with the Gregorian calender in the Julian calender month of April. The day of introduction of the Gregorian calender was made the first day of January. Some people hadn’t heard about the change in the date, so they continued to celebrate the New Year’s Day, but it being 1st April. So, others called them “April fools”.