Today is April 1st, April Fools Day. Having never heard how the day got started I decided to see what I could find using the library's Discovery Tool.
Keeping in the back of my mind that some of these articles would have been written on April Fools I looked at many, many articles and found a few origins that are believed to be possibilities.
While no one knows the exact beginnings of pulling pranks on April 1st the most widely accepted theory comes from the 16th century in France when the Gregorian calendar was introduced. This changed New Years from April 1st to January 1st. Those that continued to celebrate on the first of April were called April Fools and were invited to parties (that no one was actually throwing), sent on "fools errands", and given silly gifts.