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When a persons birthday and anniversary exist on the same day.
She spent the morning celebrating her birthday with family, and the afternoon with her boyfriend.

T'was an amaztastic birthiversary indeed!!!
by lolicakes August 11, 2010
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A Birthiversary is the other day during the year that someone officially decides to celebrate his/her birthday. For people who have birthdays on or near holidays, during an unfavorable season, or they just do not like their birthday, this provides them the opportunity to officially celebrate their birthday another time of year.
Katy's birthday is near Christmas. She officially registered her Birthiversary, now she celebrates her birthday in August because she loves the summertime!

Katy: "John, are you coming to Birthiversary party on August 15th? I'm having a pool party!!

John: "I thought your birthday is in December?"

Katy: "It is, but I chose August to officially celebrate my Birthiverary!"
by jrmoney August 27, 2011
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