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The Maya Long Count: How Mesoamerica Recorded Time

A five-position count of elapsed days, two interlocking cycles, and one unresolved correlation with our calendar. Here is how Maya dates are actually read.

By Published 6 min read

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Key takeaways

  • The Long Count is a running tally of days since a fixed base date, written in five positions that multiply by twenty at every step except one, where eighteen units make the next period up.
  • The 360-day tun is the pivot of the system: eighteen twenty-day uinals make one tun, twenty tuns make a katun, and twenty katuns make a baktun.
  • Two cycles run alongside it — a 260-day Sacred Round and a 365-day vague year — which together permute into a 52-year Calendar Round shared with other Mesoamerican peoples.
  • Converting a Long Count date to our calendar depends on a correlation that is still argued over, which is why the December 2012 cycle completion was published as the 21st, the 23rd and the 24th by different specialists.
  • Long Count dates remain working research data: a 2014 study reanalysed 89 terminal dates from Maya lowland monuments and found no support for the long-standing west-to-east collapse model.

The Long Count is a running tally of days elapsed since a fixed base date, written as five numbers separated by dots. Read left to right, those numbers are coefficients of five nested time periods, each twenty times the one below it — except at a single position, where eighteen units make the next period up. That one irregularity is deliberate, and it is what makes the system usable as a calendar rather than just a counter.

The five positions

Penn Museum's Expedition set out the structure in 1960, in an article by Linton Satterthwaite discussing what was then the earliest known Long Count date at Tikal. Maya arithmetic is built on twenty rather than ten, which is why a single position can carry a value above nine and why the numbers are written with separating dots.

Period Made of Days
Kin — 1
Uinal 20 kin 20
Tun 18 uinal 360
Katun 20 tun 7,200
Baktun 20 katun 144,000

Kin means day, and the word also means sun. Uinal probably means "twenty". The tun is the pivot: Satterthwaite calls it a sort of computing year, always 360 days, about five and a quarter days shorter than a solar year. The katun and baktun are described in that article as corresponding to our decade and century, except that they cover more time; the baktun is sometimes called a cycle.

On carved monuments the numbers appear in bar-and-dot notation — one bar for five, one dot for one — and a zero sign is used where a position is empty. That reading was first published in 1832, when Constantine Samuel Rafinesque wrote to Champollion, the decipherer of Egyptian hieroglyphs, with the conclusion that dots represented one and bars five.

The two cycles running alongside it

The Long Count fixes a date absolutely, but Maya inscriptions rarely stop there. Two repeating cycles run in parallel.

The Sacred Round combines a cycle of thirteen numbered days with a cycle of twenty named days. Because the two run concurrently, the same combination returns every 260 days. The vague year is a 365-day count of eighteen named months of twenty days each, plus an extra five-day period; it has no leap day, so it drifts against the seasons, slowly.

Run together, these permute into a 52-year Calendar Round, a structure the Maya shared with other Mesoamerican peoples. A Calendar Round date on its own is therefore ambiguous: it recurs every 52 years. That is precisely why monuments carrying serious chronological weight also carry a Long Count.

Reading a real inscription

Take the Tikal date Satterthwaite discussed: 8.12.14.8.15 13 Men 3 Zip. The Long Count portion multiplies out as

8 × 144,000 + 12 × 7,200 + 14 × 360 + 8 × 20 + 15 = 1,243,615 days

which is exactly the 3,454 tuns and 175 days the article states. The remainder of the expression, "13 Men 3 Zip", is the Calendar Round position that this many days lands on. Satterthwaite notes that this portion of the stela was almost entirely missing and that the values were reconstructed by calculation — a prediction that the stone itself would confirm if the lower half were ever found.

The base date these counts run from, written 4 Ahau 8 Cumku, was itself calculated back into the mythical past. That is a real difference from the Common Era epoch, which at least intends to mark a historical event. It also means the Long Count's zero point is a construct, not a record.

Simon Martin's 2012 overview in the same magazine gives a later example: a Calendar Round date on Copan Stela D reading 10 Ajaw 8 Ch'en, corresponding to the Long Count 9.15.5.0.0, which fell on 22 July 736 CE. Note the spellings — the 1960 article uses Ahau and Cumku, the 2012 one Ajaw and Ch'en. Orthography for Mayan languages has been standardised since, and both forms appear in the literature.

Both sites are on the UNESCO World Heritage List. Tikal is described there as inhabited from the sixth century BC to the tenth century AD; Copán's ruined citadel and public squares are described as revealing three main stages of development before the city was abandoned in the early tenth century.

The correlation problem

Converting a Long Count date into a Common Era one requires a correlation constant, and that constant is still argued over.

Martin's overview explains why. The Long Count had disappeared by the time the Spanish arrived in the Maya area around 1525, so the available clues are references to other Maya calendars left by early chroniclers and clerics. These match several Calendar Round dates to European dates of the time, and two are additionally tied to positions in the Short Count — which should fix the correlation within repeating cycles of 256 years, at which point radiocarbon evidence can select among the remaining candidates.

The alignment that best fits the evidence is known as the GMT correlation. But there are two versions of it: one consistent with survivals of the Sacred Round still in use, and one that tries to account for astronomical data in the inscriptions. That, Martin writes, is why the December 2012 cycle completion was given as the 21st by some and the 23rd by others. Many specialists favour the 23rd; the 21st is preferred by people invested in a cosmic significance for the date, because it falls on a solstice; and other evidence points to the 24th.

Satterthwaite made the same point more bluntly in 1960: saying the Tikal date falls in AD 292 is a statement according to a correlation theory which may be disputed, and choosing a different theory would not change the evidence that it was carved before any other known Long Count date at the site. The relative chronology is secure; the conversion is the contested part. That distinction between a well-attested sequence and a less certain absolute date recurs throughout chronology, and how historians date events covers how the two are kept apart.

Long Count dates as live research data

These are not antiquarian curiosities. A 2014 study in Ancient Mesoamerica reanalysed the terminal Long Count dates carved on stone monuments in the Maya lowlands — 89 of them, drawn from the Maya Hieroglyphic Database — using spatial statistics to retest a long-standing model in which large political centres were abandoned in a wave running from west to east during the Late and Terminal Classic, dated in the article to AD 730–910.

The results did not support a directional collapse. They instead indicated a contraction of Terminal Classic polities around seven core areas, with three regions showing distinct subregional ends to monument carving spread over 24 to 127 years. In other words, reading the calendar carefully changed the historical conclusion.

Placing Mesoamerican chronology beside everything else

Long Count dates are unusually good raw material for a timeline, because the inscriptions are precise and internally consistent even where the conversion is debated.

World History Timeline Sim, our own app built by Reign Creative, is useful for seeing where Maya city-states sit relative to contemporaries elsewhere — a comparison the standard curriculum rarely makes, and one our slice through the first five centuries CE takes further. Treat any displayed Common Era date for a Maya event as a conversion carrying the correlation debate inside it. The app is a tool for exploration and orientation, not a substitute for the epigraphic literature, the museum publications cited here, or the inscriptions themselves.

For the calendar machinery this sits inside, how calendars and dating systems work covers lunar, solar and lunisolar schemes generally, and how to actually learn something from a timeline app covers checking a claim you have just read. More is collected in the world history timelines hub, and our other learning tools under education and brain games.

Good to know

Frequently asked questions

What do the five numbers in a Maya date mean?
They are coefficients of five time periods, read from largest to smallest: baktun, katun, tun, uinal and kin. A kin is one day, a uinal is twenty days, a tun is eighteen uinals or 360 days, a katun is twenty tuns, and a baktun is twenty katuns. The whole expression states how many days have elapsed since a fixed base date.
Is the Maya calendar base-20?
Almost. Maya arithmetic is vigesimal, built on twenty rather than ten, and the Long Count follows that except at one position: eighteen uinals make a tun rather than twenty. That single irregularity gives a 360-day period, which sits close to the solar year and makes the higher periods behave roughly like decades and centuries.
What is the difference between the Long Count and the Calendar Round?
The Long Count is linear and never repeats, so it fixes a date absolutely. The Calendar Round is cyclical: a 260-day Sacred Round and a 365-day vague year running together return to the same combination every 52 years. A Calendar Round date alone is ambiguous across repetitions, which is why monuments that need precision carry a Long Count as well.
Why is there still an argument about converting Maya dates?
Because the Long Count had fallen out of use by the time Europeans arrived in the Maya area, so the correlation rests on a small number of matches recorded by early chroniclers, supported by radiocarbon evidence. The best-fitting alignment is known as the GMT correlation, but it exists in more than one version, and specialists differ over which is right.

Sources

  1. Maya "Long Count" Numbers (Expedition, Volume 2, Number 2, 1960) (opens in a new tab)Penn Museum (University of Pennsylvania Museum of Archaeology and Anthropology) — accessed
  2. Time, Kingship, and the Maya Universe: Maya Calendars — An Overview (Expedition, Volume 54, Number 1, 2012) (opens in a new tab)Penn Museum (University of Pennsylvania Museum of Archaeology and Anthropology) — accessed
  3. Terminal Long Count Dates and the Disintegration of Classic Period Maya Polities (Ancient Mesoamerica 25:2) (opens in a new tab)Cambridge University Press — accessed
  4. Tikal National Park (opens in a new tab)UNESCO World Heritage Centre — accessed
  5. Maya Site of Copan (opens in a new tab)UNESCO World Heritage Centre — accessed

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