2012.
What about the day after? The end of the Mayan calendar will occur when all nine cycles progress to the end of the seventh day. The day after that will be when they simultaneously change to the seventh night. Light will suddenly be replaced by Dark. Yang will be replaced by Yin.
I am sure that you can all feel the Yang building. What will happen will be Tao recoiling like s spring sprung too tight. That is what will happen.
Why will it happen? The Mayan calendar goes back 16.4 billion years, back to the Big Bang. The Universe has been expanding since then. When the Mayan calendar ends, the Universe will stop expanding and will begin contracting, probably for another 16.4 billion years.
What will it be like? Probably like a ball being thrown into the air. At the top of it's flight, it stops all motion before it begins to fall. It might be almost imperceptable. However, the change will be profound. It will go from rising to falling. The change in perception could be terrifying. Tao will still be the same, as gravity is the same.
Then what? IMO, the pattern of the Mayan calendar will operate in reverse. Things will continue to operate at a rapid pace, but, will slow over time. On the day that the calendar reverses, the Tao will be at it's quietest. It will be a great time to acheive Enlightenmant.
But then again, I am just guessing.