Judgement Day...?

Supposedly today is the last day of the world, I don't believe it. What happened in 1994 and 2000? Nothing. I want to know where these people get their facts, how do they come up with a date? I thought none of us were supposed to know when the end is supposed to come... so stop trying to predict the end of the world please. It really freaks people out, it's just a thought.