Surname Bday (Bday 
, วันเกิด 
) , all around the world, is a rare family name. The surname Bday is characteristic of Tunisia, where it is a rare surname, Thailand, where it is a very rare surname, and Malaysia, where it is an extremely rare surname. In absolute terms, it most frequently occurs in Thailand, Tunisia, and the United States. Also, Bday is the forename as well as the last name.