From Dragon Ball Encyclopedia, the ''Dragon Ball'' wiki
789 Age marked the time in which the Dragon Ball GT series began up until the conclusion of the Baby Saga. It sees the first major battles of The Grand Tour Conflict, such as Son Goku, Pan, and Trunks' adventures finding the Black Star Dragon Balls in space and the battle and victory over Baby. This year is also the second time Earth is destroyed, a result of a wish made by the Black Star Dragon Balls. Piccolo is also killed for the final time this year, a result of perishing with Earth to destroy the Black Star Dragon Balls.