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When the current day's date matches the false date of birth on your fake ID. Not knowing your fake birthday will lead to a tricky encounter with a store clerk.
*Underage kid equipped with a fake ID enters grocery store with intent on illegally buying beer. He is unaware that his fake birthday falls today. He picks up beer and places it on the counter*

Clerk - "You have ID"
Kid - " Yeah, right here"
Clerk - "Great, can I take a look?"

*kid gives ID to the clerk. Clerk takes a look*

Clerk - "this will do...Oh! Happy birthday!"
Kid - "What the fuck? It's not my birthday."

WOOOOOPS. NO BEER FOR THE KID. SHOULD HAVE KNOWN HIS FAKE BIRTHDAY.
by cbb33 January 21, 2010
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2
1. A term that certain lacrosse teams seem to think is funny to sing to a person
and tell restaurants it is their birthday when it is in reality not their birthday.

2. When someone intentionally tells someone it is their birthday to get things.
Team: "Happy Birthday to you, Julie!"
Julie: "...It's not my birthday..."
Team: "Oh but it is. Just go with it. It's your fake birthday."
by jaydawg3000 May 01, 2009
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