Unlike most of the other non-foolish holidays, the history of April Fool's Day, sometimes called All Fool's Day, is not totally clear. There really wasn't a "First Apil Fool's Day" (31). Some believe it sort of evolved simultaneously in several cultures at the same time, from celebrations involving the first day of spring.
The closest point in time that can be identified as the beginning of this tradition was in 1582, in France. Prior to that year, (32), beginning on March 25. The celebration culminated on April 1. With the reform of the calendar under Charles IX, the Gregorian calendar was introduced, (33).
However, communications being what they were in the days when news traveled by foot, (34). Others, the more obstinate crowd, refused to accept the new calendar and continued to celebrate the new year on April 1. These backward folk were labeled as "fools" by the general populace. They were subject to some ridicule, (35).
This harassment evolved, over time, (36). The tradition eventually spread to England and Scotland in the eighteenth century. It was later introduced to the American colonies of both the English and French. (37), so to speak, with different nationalities specializing in their own brand of humor at the expense of their friends and families.
In Scotland, for example, (38). The second day is devoted to pranks involving the posterior region of the body. It is called Taily Day. The origin of the “kick me” sign can be traced to this observance.
Mexico's counterpart of April Fool's day (39). Originally, the day was a sad remembrance of the slaughter of the innocent children by King Herod. It eventually evolved into a lighter commemoration involving pranks and trickery.
Pranks performed on April Fool's Day range from the simple, (such as saying, “Your shoe's untied!"), to the elaborate. Setting a roommate's alarm clock back an hour is a common gag. Whatever the prank, the trickster usually ends it (40).
(From April Fool's Day)

A. and New Year's Day was moved to January 1
B. The news media even gets involved
C. into a tradition of prank-playing on the first day of April
D. and were often sent on "fools errands" or were made the butt of other practical jokes
E. by yelling to his victim,"April Fool!"
F. many people did not receive the news for several years
G. that can be pinpointed on the calendar
H. April Fool's Day is actually celebrated for two days
I. was a fairly detailed documentary
J. the new year was celebrated for eight days
K. is actually observed on December 28
L. April Fool's Day thus developed into an international fun fest