Have your attorney (or yourself) file a Notice of Errata amendment to correct the marriage date; attached a copy of the marriage certificate to prove the correct date. A Notice of Errata allows one to correct errors “inadvertently” stated in a previously filed document. If your relationship with your ex is in good standing, ask her to sign it as well. The title can then read “Unopposed Notice of Errata”. This helps the judge grant the change.
Contact a lawyer for more details- most offer free consultations. Good luck.