Just to put this in perspective, the guy is saying that the rapture will happen at 6pm on May 21st. While it's reasonable to assume that the instant disappearance of 600+ million people all at the same time would cause a level of chaos that the world has never seen before (think planes falling out of the sky because they are without pilots, cars turning into unmanned non-guided surface-to-surface missiles, etc) it's hardly the end of the world.
That being said, the guy is considered by most of the Christian community to be a false prophet. Back in the Old Days, there was a harsh punishment for these types of people. It's called "death". Today, being that God is working amongst humankind in a different way, this isn't the standard operating procedure.
He was wrong once before on this issue back in 1994. He's back at it again and should be ashamed of himself.
God clearly stated in his word that nobody knows the day or the hour (Matthew 24:36-41) and the description of the mindest of people on that day is that they are taken completely by surprise. I don't think that this widely publicises scenerio we have going here today would conform to the type of surprise depicted by the words of Jesus Christ himself.
This guy is a false teacher who needs to repent. He may even be a false teacher that on the level of those described in Jude 14-15.