What was found
(CAN) CREW NOTICED THAT THE GPS TIME/DATE STAMP HAD RESET ITSELF TO THE ORIGINAL 1992 ALGORITHM. ONCE ACFT WOW: WENT "BLACK" ACFT, PULLED BOTH GPS C/B`S, POWERED ACFT, INITIALIZED TIME/DATE STAMP IN FMS`S, RESET GPS C/B`S. WHEN GPS`S INITIALIZED THEY WENT THROUGH SELFTEST AND CORRELATED TIME/STAMP WITH FMS ENTRY AND SYNCHED PROPERLY. PILOTS HAD TO REINSTATE "OPTIONS" SETTINGS IN FMS. CARD WAS SENT TO MFG FOR APPLICATION OF "DUAL BATTERY" MOD TO CARD.