How late can a father wait until he decides to add his name to his childs birth certificate?

If a father is not already on his childs birth certificate, how long does he have until he can add his name on there?

Most states have a declaration of parentage form that can be filed by the parent with the state agency that handles vital records or it can be a court ordered paternity adjudication. I've never heard of a time limit. Call the vital records office for your state to get the exact procedure.