Maya Time Counts

The sacred Almanac or Tzolkin, the vague year of 365 days, and the Long Count based on the tun of 360 days as unit; these three measurements combine to form the Mayan Calendar.
In a 1946 study called The Maya Correlation Problem, Maud Worcester Makemson, digs into the numbers that form each count and comes up with a very detailed but understandable explanation of how they are used in conjunction by the ancient Mayan to track time and to predict future cosmic events such has the winter solstice of 2012.

Various guesses have been made as to the origin of the Tzolkin. One suggests a connection with the lunation, another with eclipses, a third with 13 heavens and underworlds, a fourth with the interval between passages of the sun across the zenith ( right above ) in the latitude of Yucatan. Whatever it's origin, the Tzolkin........

Tzolkin, "count of days" is a synthetic Maya word applied by archeologists........we do not know the old Maya word for the period, nor for the annual count of 365 days, although the term haab is applied to the latter.....

This work is definetely worth a read...

The Maya Correlation Problem