How can i change my newborns birth certificate so i can be listed as the father?

I have a newborn who is 20 days old. My girlfriends ex thought he was the father and signed for it. We did a DNA test and it ended up i was the father. He is willing to admit hes not the father in court if it gets that far. But i read somewhere you have 45 days to change anything on the birth certificate without any paper work or a judge. So i was wondering if changing the father under that qualifys.

I live in California if that helps .How can i change my newborns birth certificate so i can be listed as the father?
Your might need court orders. Sometimes though if she goes through the attorney general to acquire child support they will include the court order for the name change. But I would check with the state agency that does the birth certificates. After all it is just a phone call to verify
The mother would need to sign off on the changes and you go through the courts for it. The "father" listed on the birthcertificate will also need to sign off on it and the courts will need a copy of the Paternity test results proving he isn't the father and that you are the father (they will need the proof you are the father, it can't just be you saying you are because he isn't so hopefully you have the test done for both of you). Any changes to it still require court approval even in the 45 day time period.How can i change my newborns birth certificate so i can be listed as the father?
You will need to go to court about it. You can't just go have it changed. Even if the man who signed the certificate isn't willing to have it changed, there is nothing he can do if you have the results of the DNA test. But, get a hold of child support and enforcement agencies and talk to them, they will be able to help more.How can i change my newborns birth certificate so i can be listed as the father?
Contact your district attorney!

They should be able to help with paperwork.