This all reminds me of William Miller and the Millerites. In 1833, he revealed the Second Coming of Christ would happen in 1843. Nobody listened at first, but eventually he built up a large group of followers, known as the Millerites. As time neared to 1843, he was pressured into revealing an exact date. The date chosen was March 21, 1843 to March 21, 1844. As that range of dates neared, the Millerites built this huge dome stadium of sorts to live in and chill out until the Rapture.
Of course, nothing happened, so they made a new date: October 22, 1844. Some Millerites kept the faith as that day passed without incident, but most either turned over to be Quakers or just tried to go back home to rebuild their lives.
These dates can be calculated in many different ways. The Bible has large use of the number 7. Many of the dates thrown out over time are figured up as a result of how they interpret certain passages and they work the numbers until they can get something relevant to the time period. Afterall, it does no good to announce the Rapture will take place on May 21, 2342.
These people are very much so fueled by the lust of attention, fame, and donations provided by followers. It's nothing new.
If you're interested in reading about a particularly fucked up religious tale, check out the book "The Kingdom of Matthias." I won't go into detail, but it's about this crazy story that actually happened in New York back in the 1830s.