Sign in to your Google Account privacy page. Click Personal info. Click Birthday.

Go to the sign in page of the product (for Google Accounts it is myaccount.google.com). Enter your Gmail username (everything that appears before '@gmail.com'). Enter your password.

The rules for correcting a birth certificate will depend on the state that originally issued your certificate. You may need to get a court order issued by a judge before the vital records office will change your date of birth. In most cases, the date on a legally-issued birth certificate is presumed to be correct.