Like certain sects of Christianity, Islam is also waiting for end times in which the 12 Imam (or madhi or messiah) will come out of hiding and return to earth.
A Wall St. Journal op-ed from August 8 (I think) linked the date that Iran was going to respond to the whole nuclear issue with the beginning of this end time.
"What is the significance of Aug. 22? This year, Aug. 22 corresponds, in the Islamic calendar, to the 27th day of the month of Rajab of the year 1427. This, by tradition, is the night when many Muslims commemorate the night flight of the prophet Muhammad on the winged horse Buraq, first to "the farthest mosque," usually identified with Jerusalem, and then to heaven and back (cf Koran XVII.1). This might well be deemed an appropriate date for the apocalyptic ending of Israel and if necessary of the world. It is far from certain that Mr. Ahmadinejad plans any such cataclysmic events precisely for Aug. 22. But it would be wise to bear the possibility in mind."
So a bunch of Christian fundies have decided that the rapture/end times are going to start today.
Only two problems with that:
A. Islam and Christianity both have completely different versions of "end times"; if this was the Islamic end time, there's no way a Rapture could/would occur because it means that Islam is correct.
B. The sacred night in question actually fell on August 21. The WSJ jackass just didn't have any idea what he was talking about.
So, basically, it's all about fear-mongering and throwing red meat to the fundies. What else is new?
On edit: here's the link to the original op-ed if you want to read it.
http://www.opinionjournal.com/extra/?id=110008768