You keep saying that. Who is feeding you such nonsense?
Well, Mithras was the son of god (Zoroaster) born of a virgin; he was worshipped on Sunday with a meal of bread and wine; he died and rose from the dead and he was prophesied to return and judge the world. His cult arose at roughly the same time as Christianity, and there is strong evidence that early Christians changed the day of worship from the Jewish sabbath to Sunday to accommodate and attract converts from Mithraism. It is widely accepted that Christianity did coopt the Dec. 25th birthday of Mithras.