The December 21, 2012 date is Uniiw (K’ank’in) 3 in the Mayan Haab Calendar
There are three dates on Monument 6 in the Tortuguero Mayan ruin in the Mexican state of Tobasco, in the Yucatan Peninsula. The “third of Uniiw (K’ank’in) refers to a date in the 365 day Mayan calendar called the “Haab.” Here’s an excerpt from Wikipedia’s online article on the Haab:
The Haab’ is part of the Maya calendric system. It was the Maya version of the 365-day calendar known to many of the pre-Columbian cultures of Mesoamerica. Unlike the Tzolk’in, another Mayan Calendar system with no obvious relation to an astronomical or geophysical cycle, the Haab’ approximated the solar year.
The Haab’ comprises eighteen “months” of twenty days each, plus an additional period of five days (“nameless days”) at the end of the year known as Wayeb’ (or Uayeb in 16th C. orthography).
