Thank God It's Doomsday
This is the 371st episode, it aired on 5/8/05
Spoiler warning
An apocalyptic movie followed by three real-life omens causes Homer to fear and begin researching the rapture. Homer deducts that the event is coming in a week and he believes the only way he can get into heaven is to warn others. A skeptical Kent Brockman does a report on Homer where Homer quotes a Biblical verse involving stars falling from the sky which later happens during a Krusty Special blimp accident. After a vision (or possibly an ice cream headache) Homer takes the new believers to Springfield Mesa and awaits a rapture that never comes. A discredited Homer returns home and discovers an error in his calculations. He then returns to the mesa alone after his friends and family turn their backs on him. At the mesa, Homer experiences the rapture (or maybe a heat induced dream) where he rampages in heaven and convinces God to delay doomsday and return Homer to his family.