The myth regarding the end of the world coming on Dec. 21st 2012, as based upon an ancient Mayan calendar is a simple mathematical conundrum, and predates the Christain (Common) Era calendar by a long shot. The Mayans didn't know of the Christ's coming birth, and they would not have likely cared.
Whether our CE calendar misrepresents the birth of this Jesus fellow or is spot on, still does not influence the Mayan multi-thousand year cycle of counting years.
It just happens that the winter solstice of 2012 in the CE (Dec. 21, 2012), was as far as their latest calendar would go to.
There were no dire forecasts for that date. :no: It was simply time for the average Mayan family to go down to the local market, and buy a new wall calendar.