According to christians, whens the world going to end?

According to Matthew that would happen while some people hearing Jesus' sermons were still alive. Some said it would happen in 1000AD. There have dozens of such dumb predictions since Christianity was invented. You do not know the Aztecs said anything about 12/31/12. Some moron said the Mayas said it happpens 12/21/12, but that is wrong. Scientists cannot coordinate the Mayan calendar with our Gregorian one, so no one can give such a precise date as 12/21/12 for the end of a cycle. I have bet several people $1000 that the world will not end 12/21/12. The Christains that I know have been saying it would be the present year since I was a boy. it looks as if they would learn eventually if they had a brain. My sister does not.