The Mesoamerican Long Count calendar is a non-repeating base-20 and base-18 calendar used by pre-Columbian Mesoamerican cultures, most notably the Maya. For this reason, it is often known as the Maya Long Count calendar. Using a modified vigesimal tally, the Long Count calendar identifies a day by counting the number of days passed since a mythical creation date that corresponds to August 11, 3114 BCE in the proleptic Gregorian calendar. The Long Count calendar was widely used on monuments.
Background The two most widely used calendars in pre-Columbian Mesoamerica were the 260-day and the 365-day . The equivalent Aztec calendars are known in Nahuatl as the and , respectively.
The combination of a and a date identifies a day in a combination which does not occur again for 18,980 days (52 cycles of 365 days equals 73 cycles of 260 days, approximately 52 years), a period known as the Calendar Round. To identify days over periods longer than this, Mesoamericans used the Long Count calendar.
Long Count periods
The Long Count calendar identifies a date by counting the number of days from a starting date that is generally calculated to be August 11, 3114 BCE in the proleptic Gregorian calendar or September 6 in the Julian calendar (or −3113 in astronomical year numbering). There has been much debate over the precise correlation between the Western calendars and the Long Count calendars. The August 11 date is based on the GMT correlation.
The completion of 13 bʼakʼtuns (August 11, 3114 BCE) marks the Creation of the world of human beings according to the Maya. On this day, Raised-up-Sky-Lord caused three stones to be set by associated gods at Lying-Down-Sky, First-Three-Stone-Place. Because the sky still lay on the primordial sea, it was black. The setting of the three stones centered the cosmos which allowed the sky to be raised, revealing the
Rather than using a base 10 scheme, the Long Count days were tallied in a modified base-20 scheme. In a pure base 20 scheme, 0.0.0.1.5 is equal to 25 and 0.0.0.2.0 is equal to 40. The Long Count is not pure base-20, however, since the second digit from the right (and only that digit) rolls over to zero when it reaches 18. Thus 0.0.1.0.0 does not represent 400 days, but rather only 360 days and 0.0.0.17.19 represents 359 days.
The name bʼakʼtun was invented by modern scholars. The numbered Long Count was no longer in use by the time the Spanish arrived in the Yucatán Peninsula, although unnumbered kʼatuns and tuns were still in use. Instead the Maya were using an abbreviated Short Count.
+ Table of Long Count units Long Count unit Long Count period Days Approximate Solar Years1 Kʼin 1 1 Winal 20 Kʼin 20 1 Tun 18 Winal 360 1 Kʼatun 20 Tun 7,200 1 Bʼakʼtun 20 Kʼatun 144,000 1 Piktun 20 Bʼakʼtun 2,880,000 1 Kalabtun 20 Piktun 57,600,000 1 Kʼinchiltun 20 Kalabtun 1,152,000,000 1 Alautun 20 Kʼinchiltun 23,040,000,000 1 Hablatun 20 Alautun 460,800,000,000
Mesoamerican numerals
Long Count dates are written with Mesoamerican numerals, as shown on this table. A dot represents 1 while a bar equals 5. The shell glyph was used to represent the zero concept. The Long Count calendar required the use of zero as a place-holder and presents one of the earliest uses of the zero concept in history.
On Maya monuments, the Long Count syntax is more complex. The date sequence is given once, at the beginning of the inscription and opens with the so-called ISIG (Introductory Series Initial Glyph) which reads tzik-a(h) habʼ [patron of Haabʼ month] ("revered was the year-count with the patron [of the month]").Boot, p. 2. Next come the 5 digits of the Long Count, followed by the Calendar Round (tzolkʼin and Haabʼ) and supplementary series. The supplementary series is optional and contains lunar data, for example, the age of the Moon on the day and the calculated length of current lunation. The text then continues with whatever activity occurred on that date.
A drawing of a full Maya Long Count inscription is shown below.
Earliest Long Counts The earliest contemporaneous Long Count inscription yet discovered is on Stela 2 at Chiapa de Corzo, Chiapas, Mexico, showing a date of 36 BCE (although this date is not certain, see table), although Stela 2 from Takalik Abaj, Guatemala might be earlier.Graham (1992, p. 331, see Fig. 5 for a line drawing of the monument) (See illustration.) Takalik Abaj Stela 2's highly battered Long Count inscription shows 7 bak'tuns, followed by k'atuns with a tentative 6 coefficient, but that could also be 11 or 16, giving the range of possible dates to fall between 236 and 19 BCE.
Although Takalik Abaj Stela 2 remains controversial, this table includes it, as well as six other artifacts with the eight oldest Long Count inscriptions according to Dartmouth professor Vincent H. Malmström (two of the artifacts contain two dates and Malmström does not include Takalik Abaj Stela 2). Note: Malmström's Gregorian dates are three or four days later than a correlation of 584283 would give (the Wikipedia table has been corrected). Interpretations of inscriptions on some artifacts differ.
Archaeological siteNameGregorian date GMT (584283) correlationLong CountLocationTakalik AbajStela 2236 – 19 BCE7.(6,11,16).?.?.?Retalhuleu, GuatemalaChiapa de CorzoStela 2December 6, 36 BCE or October 9, 182 CE7.16.3.2.13 or 8.7.3.2.13Chiapas, MexicoTres ZapotesStela CSeptember 1, 32 BCE7.16.6.16.18Veracruz, MexicoEl BaúlStela 111 – 37 CE7.18.9.7.12, 7.18.14.8.12, 7.19.7.8.12, or 7.19.15.7.12Escuintla, GuatemalaTakalik AbajStela 5August 31, 83 CE orMay 19, 103 CE8.2.2.10.15 or 8.3.2.10.15Retalhuleu, GuatemalaTakalik AbajStela 5June 3, 126 CE8.4.5.17.11Retalhuleu, GuatemalaLa MojarraStela 1May 19, 143 CE8.5.3.3.5Veracruz, MexicoLa MojarraStela 1July 11, 156 CE8.5.16.9.7Veracruz, MexicoNear La MojarraTuxtla StatuetteMarch 12, 162 CE8.6.2.4.17Veracruz, Mexico
Of the six sites, three are on the western edge of the Maya homeland and three are several hundred kilometers further west, leading some researchers to believe that the Long Count calendar predates the Maya.Diehl (2004, p. 186). La Mojarra Stela 1, the Tuxtla Statuette, Tres Zapotes Stela C and Chiapa Stela 2 are all inscribed in an Epi-Olmec, not Maya, style."A sketch of prior documentation of epi-Olmec texts", Section 5 in Peréz de Lara & Justeson (2005). El Baúl Stela 2, on the other hand, was created in the Izapan style.
The first unequivocally Maya artifact is Stela 29 from Tikal, with the Long Count date of 292 CE (8.12.14.8.15), more than 300 years after Stela 2 from Chiapa de Corzo.Coe & Koontz (2002), p. 87
More recently, with the discovery in Guatemala of the San Bartolo stone block text ( 300 BCE),Saturno et al. 2006 it has been argued that this text celebrates an upcoming time period ending celebration. This time period may have been projected to end sometime between 7.3.0.0.0 (295 BCE) and 7.5.0.0.0 (256 BCE).Giron-Abrego 2012 Besides being the earliest Maya hieroglyphic text so far uncovered, this would arguably be the earliest evidence to date of Long Count notation in Mesoamerica.
Recently at the site of El Palmar in Mexico three stelae (stelae 20, 45 and 46) were analyzed and said to hold the earliest long count date of a lowland Mayan site. The date of Stelae 46 was 8.7.1.0.0 4 Ajaw 8 Sotz (Aug. 31, AD 180 Julian). The stelae were examined combining photogrammetry and the Artec Spider II high-resolution 3D scanner.Tsukamoto K, Esparza Olguín OQ, Salazar Lama D, Campaña Valenzuela LE, Velázquez Morlet A, López Camacho J, "The Emergence of Kingship and Early Long Counts in the Maya Kingdom of El Palmar, Campeche, Mexico", Ancient Mesoamerica, pp.1-21, 2026
Latest Long Counts The Xultun Stela 10 at the site of Xultun in Guatemala, excavations in 1915 found an inscription with a Long Count date of "10.3.0.0.0 1 Ajaw 3 Yaxk’in (ad 889)", at that time the latest. Monument inscriptions at Seibal and Uaxactun in Guatemala had the same date.Zender, Marc, and Joel Skidmore. "Unearthing the Heavens: Classic Maya Murals and Astronomical Tables at Xultun, Guatemala." Mesoweb Reports, 2012 For context, the latest known long count date from Palenque is "9.18.9.4.4, corresponding to A.D. November 15, 799" (November 11 Julian GMT), on pottery.Strawinska-Zanko, Urszula, et al., "Capital in the first century: The evolution of inequality in Ancient Maya Society", Mathematical modeling of social relationships: What mathematics can tell us about people. Cham: Springer International Publishing, pp. 161-192, 2018 Inscriptions from Toniná (on a jade stone) and Tzibanche in Mexico had a long count date of "10.4.0.0.0" (January 18, 909 AD - January 13 Julian GMT).Lowe, John W. G., "The Dynamics of Apocalypse: A Systems Simulation of the Classic Maya Collapse", Albuquerque: University of New Mexico Press, 1985 The Dresden Codex has a long count date of 10.19.6.1.8" (September 25, 1210 AD - September 18 Julian GMT) though this may not be historical.Pharo, L. K., "I The Ritual Practice of Time of the Long Count Calendar of the Classic Maya Civilisation", in The Ritual Practice of Time. Leiden, The Netherlands: Brill, pp. 17–150, 2014 Other similar late long count dates have been found in the Dresden Codex, such as "10.13.13 .3.2".Vondrák, Jan, and Vladimír Böhm, "Newly found Maya records of astronomical observations in the Dresden Codex", Journal of Astronomical History and Heritage 29.1, pp. 143-159, 2026
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 Kumkʼu.All extant Maya inscriptions that represent this base date wrote it with a "13" bakʼtuns, not "0". But when using "13.0.0.0.0" as a base date in calculations, the "13" bakʼtuns has the numerical value 0, as if it were written as "0.0.0.0.0". This is easily confused when the "13" bakʼtuns has the actual value 13 in the current baktʼun, as in the Maya date for today: (=). This is referred to as a "correlation constant". The generally accepted correlation constant is the Modified Thompson 2, "Goodman–Martinez–Thompson", or GMT correlation of 584,283 days. Using the GMT correlation, the current creation started on September 6, −3113 (Julian astronomical) – August 11, 3114 BCE 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 G-M-T when talking about the correlation) were not right ..."Breaking the Maya Code, 1992, p. 114. 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. De Landa records a date that is a Tun ending in the Short Count. Oxkutzcab contains 12 Tun endings. Bricker and Bricker find that only the GMT correlation is consistent with these dates. The Book of Chilam Balam of ChumayelThe Book of Chilam Balam of Chumayel Ralph L. Roys, Washington D.C.; Carnegie Institution 1933, pp. 79, 83 contains the only colonial reference to classic long-count dates. The Julian calendar date of 11.16.0.0.0 (November 2, 1539) confirms the GMT correlation.