April Fool! In Japan, April 1 is a day of beginnings and renewals, a sort of second New Year's. It's the first day of a new school year; and the start of careers for newly hired graduates. It's also the start of a new fiscal year in business. For Japanese baseball fans, April 1 is the first day of regular season play, with celebrities throwing the first pitch.
It's also April Fools' Day, when practical jokes can be played with impunity. The tradition goes way back. One theory credits the origin of April Fools' Day to the adoption of the Gregorian calendar in 1582, when New Year's Day was officially moved from March 25 to Jan. 1. Before the change, people visited and presented gifts on the eighth day of the feast, April 1.
After the calendar change, wiseacres carrying make-believe presents made mock ceremonial visits on April 1 to fool those who had forgotten the change of date. The custom of making fools of people on April 1 continued on after its origin had been forgotten.