Terrence Mckenna on you tube will have all the info.

In short, He did a whack load of drugs that put him into a vision like state. He works off of the e-ching theory as well for correlations. He found there to be ups and downs in novelty of society, and that major turning points correlated on his graphs. He also found that time was getting sort of condensed and had patterns of recurrence. These patterns are repeating themselves only they take less and less time to achieve until you hit dec 21 2012, when they reach ZERO and stop.

Hope that helps, I may have got some wrong as I haven't watched the videos in a few years.