It's a day to be mischievous or careful.
The origins of April Fools' Day, known for its tricks and pranks, are murky. One likely explanation is April Fools was "a hazing ritual" to welcome spring, said Alex Boese, curator of the website Museum of Hoaxes.
The earliest connection of April 1 to playing tricks is documented in a 1561 poem by Flemish writer Eduard de Dene, according to Boese. In the poem a nobleman sends his servant on absurd errands on April 1. Sounds about right.