In this case it goes like this: the Mayans were really into calendars, astrology and predictions. All true. They have one calendar that ends on Dec. 21, 2012. Also true. Therefore - and here is the quantum leap in logic - even though they didn't say so, the Mayans must have been indicating that something Earth-shaking will happen when that calendar ends.
Predictions like this are nothing new. Jewish and Christian believers, spurred on by the fact that several books of the Bible claim to be prophetic, have been making prophetic claims for centuries.
In fact, you'd be hard pressed to find a time in the last few thousand years when someone wasn't proclaiming that the signs predicting that the "day of the Lord," or the return of Christ, or Armageddon, had all been fulfilled and the end of the world as we know it was coming any day now.
In the 20th Century, religious and New Age groups by the score named dates in nearly every decade, right up to the very last day of the century, as the time of the Second Coming or the Battle of Armageddon or the Rapture or the Age of Peace and Enlightenment.
There has been one thing all of these predictions have in common - they have all been wrong.
So, I'm going out on a real limb here and making a prophecy of my own. What's going to happen on Dec. 21, 2012? I'll tell you.
Nothing out of the ordinary, and certainly not the end of the world as we know it.