The one year countdown begins now. The one year countdown to what? You ask. Apparently you haven't been paying attention to John Cusak.
Some New Age types regard December 21, 2012 as the end date of a 5,125 year long cycle documented by the Mayan (or Mesoamerican) Long Count Calendar. The end of this cycle will bring at best physical and spiritual transformation of the planet and its people, or at worst total calamity, such as the Earth colliding with a passing asteroid or black hole.