T.C. is the acronym for Transcend Christ. In the year A.D. 2510, the world-wide central management organization responsible for the space emigration plan changed the current calendar from A.D. to Transcend Christ (T.C.). This calendar system is also used in the Xenogears story arc. This appears to be a surmised third step in the Gregorian dating calendar; B.C. - Before Christ, A.D. - Anno Domini (In the Year of Our Lord / During Christ), and T.C. - Transcend Christ (After Christ).