There have been many "calculations" done by various people from various Christian denominations concerning the precise date of the end of the world, like Harold Camping and 21st of May 2011. Despite those numerous instances of people figuring out the time this event was to occur, I can't find any sources to the exact math behind such claims.
Are there any resources like that available anywhere so one could verify such math and find out the flaws of the "scientific" reasoning behind them? If those are available, have they been revealed before the predicted date was to occur?