When does one become a father?

This is a literal and insignificant question. Do you become a father when your wife/girlfriend becomes pregnant (so at the point of conception), or once your child is born? Or is it something else and it's a term simply used for a man that cares for a child (If that's the case, then the answer would be my second suggestion.).


Cold, hard facts, please; nothing emotional or something stupid like, "Everyone's a father in one way or another."