S16E19 Thank God It's Doomsday
Homer gets it into his head that the end of the world is nigh and panics Springfield into believing him. There are mixed feelings when he is proved wrong. Believing he has miscalculated on the date he returns to the mountains where the next thing he knows is that he is in Heaven and the rest of the family are in Hell. After trashing Heaven he turns back time to save them but the whole thing seems to have been a dream from which the family wakes him.