| The Mesoamerican Long Count calendar is a non-repeating, vigesimal (base-20) and base-18 calendar used by several Pre-ColumbianMesoamerican cultures, most notably the Maya. For this reason, it is sometimes known as theMaya (or Mayan) 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 theGregorian calendar. The Long Count calendar was widely used on monuments. |
Background
Among other calendars devised in pre-Columbian Mesoamerica, two of the most widely used were the 365-day solar calendar (the Maya version is known as the Haab') and the 260-day calendar, with 20 periods of 13 days. In Mayan studies this 260-day calendar is known as the Tzolk'in, the equivalent Aztec calendar is known by a Nahuatl name,tonalpohualli.
The Haab' and the Tzolk'in calendars identified and named the days, but not the years. The combination of a Haab' date and a Tzolk'in date identifies a specific date in a combination which did not occur again for 52 years. The two calendars based on 365 days and 260 days repeat every 52 Haab' years, a period generally known as the Calendar Round. To designate dates over periods longer than 52 years, some Mesoamericans utilized 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 (seeCorrelations between Western calendars and the Long Count calendar section elsewhere in this article for details on correlations).
The completion of 13 b'ak'tuns (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 sun.
Rather than using a base-10 scheme, like Western numbering, the Long Count days were tallied in a base-20 and base-18 scheme. Thus 0.0.0.1.5 is equal to 25, and 0.0.0.2.0 is equal to 40. The Long Count is not consistently base-20, however, since the second digit from the right rolls over to zero when it reaches 18. Thus 0.0.1.0.0 does not represent 400 days, but rather only 360 days.
The following table shows the period equivalents as well as Maya names for these periods:
Note that the name b'ak'tun is a back-formation invented by scholars. The numbered Long Count was no longer in use by the time the Spanish arrived in the Yucatán Peninsula, although unnumbered k'atuns and tuns were still in use.
Calculating Long Count datesMaya 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.
The date on Stela C, then, is 1,125,698 days from August 11, 3114 BCE, Julian day number 1,709,981, September 1, 32 BCE in the proleptic Gregorian calendar, September 3, −31 in the Julian calendar with astronomical year numbering.
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) hab’ [patron of Haab' month] ("revered was the year-count with the patron [of the month]").Next come the 5 digits of the Long Count, followed by the tzolk'in date written as single glyph, and then by supplementary information. Most of this supplementary series is optional and has been shown to be related to lunar data, for example, the age of the moon on the day and the calculated length of current lunation.The date is concluded by a glyph stating the day and month of the Haab year. The text then continues with whatever activity occurred on that date.
Rather than using a base-10 scheme, like Western numbering, the Long Count days were tallied in a base-20 and base-18 scheme. Thus 0.0.0.1.5 is equal to 25, and 0.0.0.2.0 is equal to 40. The Long Count is not consistently base-20, however, since the second digit from the right rolls over to zero when it reaches 18. Thus 0.0.1.0.0 does not represent 400 days, but rather only 360 days.
The following table shows the period equivalents as well as Maya names for these periods:
Representation | Long Count subdivisions | Days | ~ solar years |
| 0.0.0.0.1 | 1 k'in | 1 | 1/365 |
| 0.0.0.1.0 | 1 winal = 20 k'in | 20 | 0.055 |
| 0.0.1.0.0 | 1 tun = 18 winal | 360 | 0.986 |
| 0.1.0.0.0 | 1 k'atun = 20 tun | 7,200 | 19.71 |
| 1.0.0.0.0 | 1 b'ak'tun = 20 k'atun | 144,000 | 394.3 |
Note that the name b'ak'tun is a back-formation invented by scholars. The numbered Long Count was no longer in use by the time the Spanish arrived in the Yucatán Peninsula, although unnumbered k'atuns and tuns were still in use.
Calculating Long Count dates
Mesoamerican numerals
The back of Stela C from Tres Zapotes, an Olmec archaeological site.
This is the second oldest Long Count date yet discovered. The numerals 7.16.6.16.18 translate to September 1, 32 BCE (Gregorian). The glyphs surrounding the date are what is thought to be one of the few surviving examples of Epi-Olmec script.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.
Numerical order
The Long Count dates are written vertically, with the higher periods (i.e. b'ak'tun) on the top and then the number of each successively smaller order periods until the number of days (k'in) are listed. As can be seen at left, the Long Count date shown on Stela C at Tres Zapotes is 7.16.6.16.18.
| 7 | × 144000 | = 1,008,000 days (k'in) |
| 16 | × 7200 | = 115,200 days (k'in) |
| 6 | × 360 | = 2,160 days (k'in) |
| 16 | × 20 | = 320 days (k'in) |
| 18 | × 1 | = 18 days (k'in) |
| Total days | = 1,125,698 days (k'in) |
The date on Stela C, then, is 1,125,698 days from August 11, 3114 BCE, Julian day number 1,709,981, September 1, 32 BCE in the proleptic Gregorian calendar, September 3, −31 in the Julian calendar with astronomical year numbering.
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) hab’ [patron of Haab' month] ("revered was the year-count with the patron [of the month]").Next come the 5 digits of the Long Count, followed by the tzolk'in date written as single glyph, and then by supplementary information. Most of this supplementary series is optional and has been shown to be related to lunar data, for example, the age of the moon on the day and the calculated length of current lunation.The date is concluded by a glyph stating the day and month of the Haab year. The text then continues with whatever activity occurred on that date.
