In the academic realm, there has been a continuing debate over two proposed correlations. The first we may call the 584283 correlation - named after the julian day number of its beginning date - and the second we may call the 584285 correlation. The first implies that the first day of the 13-baktun cycle of the Long Count (written 0.0.0.0.0) was August 11th, 3114 B.C.; the second, of course, is two days later. The former has the advantage of being in line with the count still being followed today. The latter was initially the best bet when formulated in 1930, but after a reappraisal of historical documents and ethnographic data, the date was shifted. Today, the 285 correlation is still being championed by Floyd Lounsbury, with Linda Schele following suit. I've examined Lounsbury's papers on this topic, and they are not convincing. Dennis Tedlock has been the best advocate pointing out the faults in Lounsbury's original paper but, with someone of Schele's stature lending support - apparently without any close scrutiny of the matter - has created a distressing situation. A note from my article "The How and Why of the Mayan End Date in A.D. 2012" (Dec '94) clarifies the problem:
"Linda Schele and David Freidel, unlike most Mayanists, continue to support the work of Floyd Lounsbury in promoting the 584285 correlation. This is 2 days off from the Thompson correlation that I use. The decisive factor in supporting the Thompson correlation of 584283 is the fact that it corresponds with the tzolkin count still followed in the highlands of Guatemala. To account for this discrepency in his correlation, Lounsbury claims that the count was shifted back two days sometime before the conquest (not likely), thus explaining its present placement. This means that either correlation will give the December 21st end date. Nevertheless, Schele and Freidel still report that the end date is December 23rd, 2012 rather than Dec. 21st, an unfortunate faux pas understandable only because they aren't particularly interested in the specifics of the correlation debate. For a detailed discussion of this topic, refer to my book Tzolkin: Visionary Perspectives and Calendar Studies (59).
The entire problem is complex, yet clearly solvable. I explored the correlation question in Chapter Two of my book Tzolkin: Visionary Perspectives and Calendar Studies (1994), and an excerpt follows this brief intro. In an unpublished paper from 1993, I also exposed the fallacy of Lounsbury's 1992 argument which appeared in The Sky in Mayan Literature.
There is good software available with which the student of Mayan calendrics can track the tzolkin, Long Count, haab and other Mayan time cycles. For the convenience of visitors to my website, I provide simple tzolkin correlations on a monthly basis. These dates correspond to the count still be followed by daykeepers among the Quiche, Ixil, Tzutujil and other Mayan groups today.
The correlation question is probably the most fundamental and difficult one that Mayan scholars have struggled with. Once answered, an exact comparison between Mayan dates and the Gregorian calendar can be made. But the problem is complex.
Most of the stelae inscriptions in the archeological record contain Long Count dates alongside tzolkin/haab dates. For example, the ruler Chan-Bahlum of Palenque dedicated the Group of the Cross Complex and performed rituals on 22.214.171.124.16 2 Cib 14 Mol. Knowing this, we can calculate backwards to find the tzolkin/haab date which corresponds to the base date of the Long Count (the days previous to the date given above are 126.96.36.199.15 1 Men 13 Mol, 188.8.131.52.14 13 Ix 12 Mol, 184.108.40.206.13 12 Ben 11 Mol, and so on). In this way, the tzolkin/haab date which corresponds to 0.0.0.0.0 in the Long Count is 4 Ahau 8 Cumku. In addition, the majority of dates from the archeological record are internally consistent; they all lead back to 4 Ahau 8 Cumhu. This is the mythological starting point of the Great Cycle of 13 Baktuns. But we still haven't correlated this base date with a European time-frame. We don't know whether Chan-Bahlum dedicated those temples before the Battle of Hastings, or before the Roman Empire. Archeological dating methods alone have helped to estimate the time of a kingdom's existence, yet the urge to pinpoint an exact correlation has belabored many scholars. What they were looking for became known as "the Ahau equation" or the "correlation constant." This would be the Julian Day number which corresponds to the base date of the Long Count, thereby providing a link with the Gregorian calendar. For the sake of brevity, I will usually refer to this as the "corr #".
Many noted Mayan scholars have worked on this problem, in addition to their work in related fields. Tozzer, Spinden, Morley, Teeple and Thomspon all contributed to the foundation which eventually enabled the "corr #" to be discovered. But it was a long and well scrutinized process.
The first approach was to identify eclipse glyphs alongside Long Count and tzolkin/haab dates, and try to find likely candidates in the Gregorian calendar by way of modern astronomical data. In his book Maya Civilization the great Mayanist J. Eric S. Thompson had a more ambitious idea. He figured that if an exact correlation could be made, by way of comparing inscription glyphs with astronomical events, he could identify the glyphs which referred to the planets and various phenomena such as eclipses, conjunctions and solstices. Indeed, a precise correlation has in recent years helped to decipher many hieroglyphs. But the astronomical approach, by itself, was lacking.
Contributions from other fields of research soon required any proposed correlation constant to accord with several different considerations; ethnohistorical, archeological, and astronomical. The crucial ethnohistorical documents include the survivingMayan books such as the Grolier, Madrid and Dresden Codices, as well as post-conquest writings from the Yucatan. Over the years, corr #'s have ranged from J.D. 394,483 (Bowditch:1910) to 774,083 (Vaillant:1935). This implies a beginning point of the Great Cycle as long ago as 3634 B.C and as recently as 2594 B.C. By 1930, almost a dozen proposals had already been forwarded, when Thompson came up with his 584285 corr #. It was based primarily on three cross-referenced documents from post conquest Yucatan. These were: the Chronicle of Oxcutzcab, the Book of Chilam Balam, and the writings of Bishop Diego de Landa. The Chronicle of Oxcutzcab states that a tun ended on 13 Ahau 8 Xul in the year 1539 (Teeple 1930:101). The book of Chilam Balam places an indigenous calendar next to the Julian one used by the Spaniards, indicating that February 15th, 1544 = 11 Chuen 18 or 19 Zac. Landa's records place July 16th, 1553 across from 12 Kan 2 Pop. (This was later realized to have been off by one day, as Landa neglected to count the leap year day of Feb 29th 1552.)
In Skywatchers of Ancient Mexico, Anthony Aveni relates that this assembled evidence makes 220.127.116.11.0 (the tun ending spoken of above) fall on November 3rd, 1539 (Aveni 1980:207). The 18.104.22.168.0 Long Count date indicates that it was not only a tun ending, but a katun ending as well. The original Thompson corr # was equal to J.D. 584285. Since then, ethnographic data from the Highlands of Guatemala and the re-appraisal of the documents reviewed above give us the slightly adjusted "Thompson 2" correlation, otherwise known as the Goodman-Martinez-Thompson correlation (the GMT), in which the base of the Long Count is J.D. 584283 (Satterthwaite 1965:628).
It seems that scholars had a free for all with this question, and that multitudes of justifiable "solutions" could be generated from the vast field of data.
The GMT has survived decades of interdisciplinary testing and seems to be the one with the most support, although there are still scholars who question its validity. Judith Ann Remington writes in an article of hers which appeared in Archeoastronomy in the Americas that, "actually, the GMT correlation does not fit the astronomical evidence very well. It usually requires a fairly major "ammendment" of the [Venus Table] text [of the Dresden Codex]"(198). She continues, relating that when the Carbon 14 dating process became available, it supported the Spinden correlation (489,383), and that "the GMT correlation was accepted perfunctorily at a time when the Spinden correlation was being rejected because of Spinden's "ungentlemanly ways"" (200).
But years before this attack, Thompson had already defended his position against the initial Carbon 14 data. The Carbon 14 method was applied to archeological dating soon after its discovery, and Thompson writes that, "The uncritical acceptance of the new [Carbon 14] process savored too much of dancing round the Golden Calf for my liking" (191). It was soon found that more extensive testing was needed to obtain accurate results. Finally, a new Carbon 14 gas-analysis technique was developed. From Maya Civilization we read:
"In 1959 the University of Pennsylvania ran 33 counts of samples from ten beams in a Tikal temple. The whole series averaged out to A.D. 746 with a leeway of 34 years on either side. These beams were carved with a Maya date which is equivalent of A.D. 741 in the GMT correlation... the equivalent in the Spinden correlation is A.D. 481" (40-41).
Overwhelming support for the precise placement of the Thompson corr # (the GMT) came in the 40' and 50's, when newly discovered calendar counts still being followed among the Quiche, Kekchi and Ixil of Guatemala all supported the 584283. Any suspected break in the Calendar count between the time of the conquest and recent findings is highly unlikely; they all accurately project backward to dates from the Aztec and Yucatec conquest. As far as the surviving counts of Guatemala go to support proposed correlations, they do indeed all support the GMT:584283. But they would also support any correlation that was different from the GMT by a multiple of the 260-day cycle. It turns out the Bowditch (1910), the Vaillant (1935) and the Spinden (1930) are. But the archeological evidence related by Thompson seems to supercede this fact. When the interdisciplinary approach is fully considered, the GMT seems to be the best bet right now. A review of my source material used in this book demonstrates the support for the 584283.
And yet, the debate still continues among an important group of scholars (see the last 2 sources in the table listed above). In "The Base of the Venus Table of the Dresen Codex, and it's Significance for the Calendar Correlation Problem", Floyd G. Lounsbury demonstrates support for the original value of the Thompson correlation (1930), which is 584285. Regardless of flawless reasoning and detailed charts, the astronomical basis of his argument does not provide an accuracy within a 2 day range. Dennis Tedlock relates in the notes to his translation of the Popol Vuh that Lounsbury's astronomical argument could easily be two days off. Astronomer John B. Carlson concurs.
Another study also refutes the implied 2-day shift. In 1988, Munro Edmonson published an exhaustive study of the calendar systems of Mesoamerica, showing the universal uniformity of all the calendar counts. This means that if it was the day 6 Coatl (serpent) to the Aztecs of Central Mexico, it was 6 Chicchan (serpent) to the Maya of the Yucatec, and 6 Kan (serpent) to the Quiche of Guatemala, something that demonstrates the amazing sophistication of preconquest Mesoamerican civilization. He discusses the Yucatec documents and concludes that the 584283 correlation is the correct one. Furthermore, Edmonson goes on to say that no other correlation is "No other solution is ethnohistorically possible without postulating a break in the continuity and uniformity of the universal Middle American day count" (249). Such a position is countered by every date in Edmonson's study.
And this is exactly what Lounsbury suggests in his paper, which has many other merits. He uses a brilliant argument that, in fact, applies to a completely different thesis, to validate his support of the 584285. Let's look a little closer at Lounsbury's paper, wade through the technical jargon and try to decipher exactly what is said.