Bah, humbug to you all! Off to the workhouses!
Well, the Mayans were off by say, 1,000,000,000 years!
(I don't know the answers either, but said that statement above to show that nobody's perfect.)
Apropos of nothing I was reading a book about Mayan archaeology a few weeks before "The End", the book dealt with some of the latest understanding of how Mayans reckoned time, and to say 21 December 2012 was the end of things was a quite old understanding of the Mayan Long Count. Baktuns, katuns and the like are just a SMALL subset of how the Mayans actually did their calendar calculations.
In a nutshell the author said when looking at the entirety of the Mayan calendar system they looked at cycles of 10s of billions of years, not the thousands the doom and gloom crowd were using to sell videos and books.