The first day of the month, where pranks and practical jokes are played. Similar to April Fools, except that it comes once a month instead of once a year.
James: WTF!?! You told the boss I was playing hookie all day?
Todd: September Fools Day!
by seththegreat September 1, 2010
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The one day when it's okay to be a complete and total asshole.
"Mom, I'm pregnant!"

"You're only fifteen." **has a heart attack**

"...Happy April Fool's Day..."
by jaycubed31 April 1, 2009
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The one day of the year where nobody, no matter how hard they try, can possibly be funny.
Hey man, you want some peanuts? (Snake flies out of can) April fools!
by Basil April 1, 2005
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Trust no one... you are not safe. Run And hide. Don't try to defend your self you WILL FAIL.
Jim didn't run or hide so he was pranked on April Fools Day
by Urban_Dictionary_Daily247 April 1, 2015
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The absolute best possible day to celebrate one of the most unlikely, unsubstantiated and ecumenically contrived events in the whole of religious history.
easter falls on the first day of april.
Isn't that also April fools Day?
It was. NOW it's Easter fooles day!
by YAWA January 25, 2018
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12/21/12

They sure got us good
The Mayans were the original pranksters. They set up a prank so good, that over 5000 years later, it fooled millions of stupid people into thinking the world was going to end. December 21st 2012, otherwise known as Mayan Fools Day.

Mayan King: Dood check this out, I told our wisemen to make a calendar with the sole purpose of screwing with people thousands of years from now. They will think that the end of the calendar means the end of the world!

Mayan Dood: Haha, that good prank. People in the future so stupid, they believe anything.

Mayan King: Haha, indeed. I'm going to eat your heart now.
by MattSwrotethis December 21, 2012
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