Mesoamerican Long Count Calendar - Correlations Between Western Calendars and The Long Count

Correlations Between Western Calendars and The Long Count

The Maya and Western calendars are correlated by using a Julian day number (JDN) of the starting date of the current creation – 13.0.0.0.0, 4 Ajaw, 8 Kumk'u. This is referred to as a correlation constant. The generally accepted correlation constant is the Modified Thompson 2, "Goodman, Martinez, Thompson" – GMT correlation of 584,283 days. ("GMT" is an acronym of their names; is not to be confused with Greenwich Mean Time.) Using the GMT correlation, the current creation started on September 6, 3114 BC (in the Julian Calendar — not to be confused with Julian day number), August 11 in the Proleptic Gregorian calendar. The study of correlating the Maya and western calendar is referred to as the correlation question. The GMT correlation is also called the 11.16 correlation.

In Breaking the Maya Code, Michael D. Coe writes: "In spite of oceans of ink that have been spilled on the subject, there now is not the slightest chance that these three scholars (conflated to GMT when talking about the correlation) were not right...". The evidence for the GMT correlation is historical, astronomical, and archaeological:

Historical: Calendar Round dates with a corresponding Julian date are recorded in Diego de Landa's Relación de las cosas de Yucatán (written circa 1566), the Chronicle of Oxcutzkab and the books of Chilam Balam. Oxcutzkab and de Landa record a date that is a Tun ending. Regarding these historical references in The Skywatchers Aveni writes: "All the assembled data are consistent with the equation November 2, 1539 = 11.16.0.0.0. Thus for the GMT, or 11.16 correlation we find that A = 584,283...". The fall of the capital city of the Aztec Empire, Tenochtitlan, occurred on August 13, 1521. A number of different chroniclers wrote that this was a Tzolk'in (Tonalpohualli) of 1 Snake. Post-conquest scholars such as Sahagun and Duran recorded Aztec calendar dates with a calendar date. Many indigenous communities in the Mexican states of Veracruz, Oaxaca and Chiapas and in Guatemala, principally those speaking the Mayan languages Ixil, Mam, Pokomchí, and Quiché, keep the Tzolk'in and in many cases the Haab'. These are all consistent with the GMT correlation.

Astronomical: Any correct correlation must match the astronomical content of classic inscriptions. The GMT correlation does an excellent job of matching lunar data in the supplementary series. For example: An inscription at the Temple of the Sun at Palenque records that on Long Count 9.16.4.10.8 there were 26 days completed in a 30 day lunation. This Long Count is also the entry date for the eclipse table of the Dresden Codex which gives eclipse seasons when the Moon is near its ascending or descending node and an eclipse is likely to occur. Dates converted using the GMT correlation fall roughly in this eclipse season. The Dresden Codex contains a Venus table which records the heliacal risings of Venus. The GMT correlation agrees with these to within a few days which is as accurately as these could have been observed by the ancient Maya.

Archaeological: Various items that can be associated with specific Long Count dates have been isotope dated. In 1959 the University of Pennsylvania carbon dated samples from ten wood lintels from Tikal. These were carved with a date equivalent to 741 AD, using the GMT correlation. The average carbon date was 746±34 years.

If a proposed correlation only has to agree with one of these lines of evidence there could be numerous other possibilities. Astronomers have proposed many correlations, for example: Lounsbury, Fuls, et al., Böhm and Böhm and Stock.

Today, 14:26, Sunday January 27, 2013 (UTC), in the Long Count is 13.0.0.1.17 (GMT correlation).