April fools day 

1. April 1st 
2. that day people tries to prank someone else 
3. The most common theory about the earliest April Fools’ celebrations goes like this: In 1582, Pope Gregory XIII issued a papal bull decreeing a new standard calendar for Christian Europe that would take his name and centuries later become the standard internationally in the 21st century.
4. you can do pranks on them but you  cant play dirty 
5. As April Fools' is celebrated in different ways throughout the world, it is unknown exactly how the tradition originated. Some cultures saw it as the first day of spring, celebrating with general merriment and feasting, and certain calendars may consider it the first day of the year. One theory for the terming of an April Fool was that some refused to follow these calendars that recognized April 1st as the first day of the year, which resulted in being called an April Fool.