MolDx website states that transition to MolDx rules in Jurisdiction J (former Cahaba = TN GA AL) was in June 2018.
5. Is the MolDX Program national in scope?
The MolDX Program currently covers JE (American Samoa, Calif., Guam, Hawaii, Nev., North Mariana Islands), JF (Ark., Ariz., Idaho, Mont., N.D., Ore., S.D., Utah, Wash., Wyo.), JM (N.C., S.C., Va., W.Va.), J15 (Ky., Ohio), JJ (Tenn., Ga., Ala.) J5 (Iowa, Mo., Kan., Nev.), and J8 (Mich., Ind.). The role-out of JJ [Jurisdiction J] by Palmetto GBA began in early 2018. Labs that perform services for patients in those states have been notified to begin DEX Z-Code registration. Claims submitted after June 1, 2018, must have a Z-Code.
I also saw this date mentioned in a coding compliance article from that period.