Welcome to the Search and Reunion Message Board!
Fortunately California is not one of those states that changed the date of birth between the original birth certificate and the amended birth certificate if the birth and adoption both happened in California. There may be some exceptions to this but so far I have not found an altered birth date.
California Search Website:
http://www.adoptionforums.com
http://www.adoptionchat.com
http://www.adoptionlists.com
http://www.adoption.com
http://www.adopting.org
http://www.adoptionregistry.com