Thank God It's Doomsday The Simpsons : Season 16 Episode 19

Homer sees a movie about the end of the world and fears the same thing will happen in real life after seeing a chain of random occurrences (celebrities ["stars"] falling from the sky, raining blood, a man in a realistic devil costume) and doing a complicated math equation that predicts the end will come on May 18th, but when the end does not come, Homer discovers a flaw in the equation and ends up in Heaven where he meets God and learns that God is planning The Rapture.