Maya calendar

The Maya calendar is a system of calendars used in pre-Columbian Mesoamerica, and in many modern communities in highland Guatemala and in Veracruz, Oaxaca and Chiapas, Mexico.

The essentials of the Maya calendar are based upon a system which had been in common use throughout the region, dating back to at least the 5th century BCE. It shares many aspects with calendars employed by other earlier Mesoamerican civilizations, such as the Zapotec and Olmec, and contemporary or later ones such as the Mixtec and Aztec calendars. Although the Mesoamerican calendar did not originate with the Maya, their subsequent extensions and refinements of it were the most sophisticated. Along with those of the Aztecs, the Maya calendars are the best-documented and most completely understood.

By the Maya mythological tradition, as documented in Colonial Yucatec accounts and reconstructed from Late Classic and Postclassic inscriptions, the deity Itzamna is frequently credited with bringing the knowledge of the calendar system to the ancestral Maya, along with writing in general and other foundational aspects of Maya culture.

Overview

The Maya calendar consists of several cycles or counts of different lengths.

The 260-day count is known to scholars as the Tzolkin, or Tzolk'in in the revised orthography of the Academia de las Lenguas Mayas de Guatemala. The Tzolk'in was combined with a 365-day vague solar year known as the Haab' to form a synchronized cycle lasting for 52 Haab', called the Calendar Round. Smaller cycles of 13 days (the trecena) and 20 days (the veintena) were important components of the Tzolk'in and Haab' cycles, respectively. The Calendar Round is still in use by many groups in the Guatemalan highlands.

A different calendar was used to track longer periods of time, and for the inscription of calendar dates (i.e., identifying when one event occurred in relation to others). This is the Long Count. It is a count of days since a mythological starting-point. According to the correlation between the Long Count and Western calendars accepted by the great majority of Maya researchers (known as the Goodman-Martinez-Thompson, or GMT, correlation), this starting-point is equivalent to August 11, 3114 BCE in the proleptic Gregorian calendar or 6 September in the Julian calendar (−3113 astronomical). The GMT correlation was chosen by John Eric Sydney Thompson in 1935 on the basis of earlier correlations by Joseph Goodman in 1905 (August 11), Juan Martínez Hernández in 1926 (August 12), and Thompson himself in 1927 (August 13). By its linear nature, the Long Count was capable of being extended to refer to any date far into the past or future. This calendar involved the use of a positional notation system, in which each position signified an increasing multiple of the number of days. The Maya numeral system was essentially vigesimal (i.e., base-20), and each unit of a given position represented 20 times the unit of the position which preceded it. An important exception was made for the second-order place value, which instead represented 18 × 20, or 360 days, more closely approximating the solar year than would 20 × 20= 400 days. It should be noted however that the cycles of the Long Count are independent of the solar year.

Many Maya Long Count inscriptions contain a supplementary series, which provides information on the lunar phase, number of the current lunation in a series of six and which of the nine Lords of the Night rules.

A 584-day Venus cycle was also maintained, which tracked the heliacal risings of Venus as the morning and evening stars. Many events in this cycle were seen as being astrologically inauspicious and baleful, and occasionally warfare was astrologically timed to coincide with stages in this cycle.

Less-prevalent or poorly understood cycles, combinations and calendar progressions were also tracked. An 819-day Count is attested in a few inscriptions. Repeating sets of 9-day (see below "Nine lords of the night")associated with different groups of deities, animals, and other significant concepts are also known.

However, and in common with other Mesoamerican societies, the repetition of the various calendric cycles, the natural cycles of observable phenomena, and the recurrence and renewal of death-rebirth imagery in their mythological traditions were important influences upon Maya societies. This conceptual view, in which the "cyclical nature" of time is highlighted, was a pre-eminent one, and many rituals were concerned with the completion and re-occurrences of various cycles. As the particular calendric configurations were once again repeated, so too were the "supernatural" influences with which they were associated. Thus it was held that particular calendar configurations had a specific "character" to them, which would influence events on days exhibiting that configuration. Divinations could then be made from the auguries associated with a certain configuration, since events taking place on some future date would be subject to the same influences as its corresponding previous cycle dates. Events and ceremonies would be timed to coincide with auspicious dates, and avoid inauspicious ones.

The completion of significant calendar cycles ("period endings"), such as a k'atun-cycle, were often marked by the erection and dedication of specific monuments (mostly stela inscriptions, but sometimes twin-pyramid complexes such as those in Tikal and Yaxha), commemorating the completion, accompanied by dedicatory ceremonies.

A cyclical interpretation is also noted in Maya creation accounts, in which the present world and the humans in it were preceded by other worlds (one to five others, depending on the tradition) which were fashioned in various forms by the gods, but subsequently destroyed. The present world also had a tenuous existence, requiring the supplication and offerings of periodic sacrifice to maintain the balance of continuing existence. Similar themes are found in the creation accounts of other Mesoamerican societies.

Tzolk'in

Main article: Tzolk'in

The tzolk'in (in modern Maya orthography; also commonly written tzolkin) is the name commonly employed by Mayanist researchers for the Maya Sacred Round or 260-day calendar. The word tzolk'in is a neologism coined in Yucatec Maya, to mean "count of days" (Coe 1992). The various names of this calendar as used by precolumbian Maya peoples are still debated by scholars. The Aztec calendar equivalent was called Tonalpohualli, in the Nahuatl language.

The tzolk'in calendar combines twenty day names with the thirteen numbers of the trecena cycle to produce 260 unique days. It is used to determine the time of religious and ceremonial events and for divination. Each successive day is numbered from 1 up to 13 and then starting again at 1. Separately from this, every day is given a name in sequence from a list of 20 day names:

Tzolk'in calendar: named days and associated glyphs

Seq. Num. 1	Day Name 2	Glyph example 3	16th C. Yucatec 4	reconstructed Classic Maya 5	Seq. Num. 1	Day Name 2	Glyph example 3	16th C. Yucatec 4	reconstructed Classic Maya 5
01	Imix'		Imix	Imix (?) / Ha' (?)	11	Chuwen		Chuen	(unknown)
02	Ik'		Ik	Ik'	12	Eb'		Eb	(unknown)
03	Ak'b'al		Akbal	Ak'b'al (?)	13	B'en		Ben	C'klab
04	K'an		Kan	K'an (?)	14	Ix		Ix	Hix (?)
05	Chikchan		Chicchan	(unknown)	15	Men		Men	(unknown)
06	Kimi		Cimi	Cham (?)	16	K'ib'		Cib	(unknown)
07	Manik'		Manik	Manich' (?)	17	Kab'an		Caban	Chab' (?)
08	Lamat		Lamat	Ek' (?)	18	Etz'nab'		Etznab	(unknown)
09	Muluk		Muluc	(unknown)	19	Kawak		Cauac	(unknown)
10	Ok		Oc	(unknown)	20	Ajaw		Ahau	Ajaw
NOTES: The sequence number of the named day in the Tzolk'in calendar Day name, in the standardized and revised orthography of the Guatemalan Academia de Lenguas Mayas An example glyph (logogram) for the named day. Note that for most of these several different forms are recorded; the ones shown here are typical of carved monumental inscriptions (these are "cartouche" versions) Day name, as recorded from 16th century Yukatek Maya accounts, principally Diego de Landa; this orthography has (until recently) been widely used In most cases, the actual day name as spoken in the time of the Classic Period (ca. 200–900) when most inscriptions were made is not known. The versions given here (in Classic Maya, the main language of the inscriptions) are reconstructed on the basis of phonological evidence, if available; a '?' symbol indicates the reconstruction is tentative.

Some systems started the count with 1 Imix', followed by 2 Ik', 3 Ak'b'al, etc. up to 13 B'en. The trecena day numbers then start again at 1 while the named-day sequence continues onwards, so the next days in the sequence are 1 Ix, 2 Men, 3 K'ib', 4 Kab'an, 5 Etz'nab', 6 Kawak, and 7 Ajaw. With all twenty named days used, these now began to repeat the cycle while the number sequence continues, so the next day after 7 Ajaw is 8 Imix'. The repetition of these interlocking 13- and 20-day cycles therefore takes 260 days to complete (that is, for every possible combination of number/named day to occur once).

Origin of the Tzolk'in

The exact origin of the Tzolk'in is not known, but there are several theories.

• One theory is that the calendar came from mathematical operations based on the numbers thirteen and twenty, which were important numbers to the Maya. The numbers multiplied together equal 260.
• Another theory is that the 260-day period came from the length of human pregnancy. This is close to the average number of days between the first missed menstrual period and birth, unlike Naegele's rule which is 40 weeks (280 days) between the last menstrual period and birth. It is postulated that midwives originally developed the calendar to predict babies' expected birth dates. The deity Ix Chel is thus of particular interest due to her mythic relation to the calendar.
• A third theory comes from understanding of astronomy, geography and archaeology. The mesoamerican calendar probably originated with the Olmecs, and a settlement existed at Izapa, in southeast Chiapas Mexico, before 1200 BC. There, at a latitude of about 15° N, the Sun passes through zenith twice a year, and there are 260 days between zenithal passages, and gnomons (used generally for observing the path of the Sun and in particular zenithal passages), were found at this and other sites.

• A fourth theory is that the calendar is based on the crops. From planting to harvest is approximately 260 days.

Haab'

Haab' months: names and glyphs in sequence

Seq. Num.	Yucatec name	Hieroglyph	Meaning of glyph	Seq. Num.	Yucatec name	Hieroglyph	Meaning of glyph
1	Pop		mat	10	Yax		green storm
2	Wo'		black conjunction	11	Sak'		white storm
3	Sip		red conjunction	12	Keh		red storm
4	Sotz'		bat	13	Mak		enclosed
5	Sek		watering time	14	K'ank'in		yellow sun
6	Xul		dog	15	Muwan'		owl
7	Yaxk'in'		new sun	16	Pax		planting time
8	Mol		water	17	K'ayab		turtle
9	Ch'en		black storm	18	Kumk'u		granary
				19	Wayeb'		five unlucky days

Main article: Haab'

The Haab' was the Maya solar calendar made up of eighteen months of twenty days each plus a period of five days ("nameless days") at the end of the year known as Wayeb' (or Uayeb in 16th C. orthography). The five days of Wayeb', were thought to be a dangerous time. Foster (2002) writes, "During Wayeb, portals between the mortal realm and the Underworld dissolved. No boundaries prevented the ill-intending deities from causing disasters." To ward off these evil spirits, the Maya had customs and rituals they practiced during Wayeb'. For example, people avoided leaving their houses and washing or combing their hair. Bricker (1982) estimates that the Haab' was first used around 550 BC with a starting point of the winter solstice.

The Haab' month names are known today by their corresponding names in colonial-era Yukatek Maya, as transcribed by 16th century sources (in particular, Diego de Landa and books such as the Chilam Balam of Chumayel). Phonemic analyses of Haab' glyph names in pre-Columbian Maya inscriptions have demonstrated that the names for these twenty-day periods varied considerably from region to region and from period to period, reflecting differences in the base language(s) and usage in the Classic and Postclassic eras predating their recording by Spanish sources.

Each day in the Haab' calendar was identified by a day number in the month followed by the name of the month. Day numbers began with a glyph translated as the "seating of" a named month, which is usually regarded as day 0 of that month, although a minority treat it as day 20 of the month preceding the named month. In the latter case, the seating of Pop is day 5 of Wayeb'. For the majority, the first day of the year was 0 Pop (the seating of Pop). This was followed by 1 Pop, 2 Pop as far as 19 Pop then 0 Wo, 1 Wo and so on.

As a calendar for keeping track of the seasons, the Haab' was a bit inaccurate, since it treated the year as having exactly 365 days, and ignored the extra quarter day (approximately) in the actual tropical year. This meant that the seasons moved with respect to the calendar year by a quarter day each year, so that the calendar months named after particular seasons no longer corresponded to these seasons after a few centuries. The Haab' is equivalent to the wandering 365-day year of the ancient Egyptians.

Calendar Round

A Calendar Round date is a date that gives both the Tzolk'in and Haab'. This date will repeat after 52 Haab' years or 18,980 days, a Calendar Round. For example, the current creation started on 4 Ahau 8 Kumk'u. When this date recurs it is known as a Calendar Round completion.

Arithmetically, the duration of the Calendar Round can be explained in various ways. One way is to consider that the least common multiple of 260 and 365 is 18980 (73 X 260 Tzolk’in days equalling 52 X 365 Haab’ days).

Not every possible combination of Tzolk'in and Haab' can occur. For Tzolk'in days Imix, Kimi, Chwen and Kib', the Haab' day can only be 4, 9, 14 or 19; for Ik', Manik', Eb' and Kab'an, the Haab' day can only be 0, 5, 10 or 15; for Akb'al', Lamat, B'en and Etz'nab', the Haab' day can only be 1, 6, 11 or 16; for K'an, Muluk, Ix and Kawak, the Haab' day can only be 2, 7, 12 or 17; and for Chikchan, Ok, Men and Ajaw, the Haab' day can only be 3, 8, 13 or 18.

Year Bearer

A "Year Bearer" is a Tzolk'in day name that occurs on the first day of the Haab'. If the first day of the Haab' is 0 Pop, then each 0 Pop will coincide with a Tzolk'in date, for example, 1 Ik'  0 Pop. Since there are twenty Tzolk'in day names and the Haab' year has 365 days (20*18 + 5), the Tzolk'in name for each succeeding Haab' zero day will be incremented by 5 in the cycle of day names like this:

1 Ik'   0 Pop
2 Manik'   0 Pop
3 Eb'   0 Pop
4 Kab'an   0 Pop
5 Ik'   0 Pop...

Only these four of the Tzolk'in day names can coincide with 0 Pop, and these four are called the "Year Bearers".

"Year Bearer" literally translates a Mayan concept. Its importance resides in two facts. For one, the four years headed by the Year Bearers are named after them and share their characteristics; therefore, they also have their own prognostications and patron deities. Moreover, since the Year Bearers are geographically identified with boundary markers or mountains, they help define the local community.

The classic system of Year Bearers described above is found at Tikal and in the Dresden Codex. During the Late Classic period a different set of Year Bearers was in use in Campeche. In this system, the Year Bearers were the Tzolk'in that coincided with 1 Pop. These were Ak'b'al, Lamat, B'en and Edz'nab. During the Post-Classic period in Yucatán a third system was in use. In this system the Year Bearers were the days that coincided with 2 Pop: K'an, Muluc, Ix and Kawak. This system is found in the Chronicle of Oxkutzcab. In addition, just before the Spanish conquest in Mayapan the Maya began to number the days of the Haab' from 1 to 20. In this system the Year Bearers are the same as in the 1 Pop - Campeche system. The Classic Year Bearer system is still in use in the Guatemalan highlands and in Veracruz, Oaxaca and Chiapas, Mexico.

Long Count

East side of stela C, Quirigua with the mythical creation date of 13 baktuns, 0 katuns, 0 tuns, 0 uinals, 0 kins, 4 Ahau 8 Cumku - August 11, 3114 BCE in the proleptic Gregorian calendar.

Main article: Mesoamerican Long Count calendar

Since Calendar Round dates repeat every 18,980 days, approximately 52 solar years, the cycle repeats roughly once each lifetime, so a more refined method of dating was needed if history was to be recorded accurately. To specify dates over periods longer than 52 years, Mesoamericans used the Long Count calendar.

The Maya name for a day was k'in. Twenty of these k'ins are known as a winal or uinal. Eighteen winals make one tun. Twenty tuns are known as a k'atun. Twenty k'atuns make a b'ak'tun.

The Long Count calendar identifies a date by counting the number of days from the Mayan creation date 4 Ahaw, 8 Kumk'u (August 11, 3114 BC in the proleptic Gregorian calendar or September 6 in the Julian calendar). But instead of using a base-10 (decimal) scheme like Western numbering, the Long Count days were tallied in a modified base-20 scheme. Thus 0.0.0.1.5 is equal to 25, and 0.0.0.2.0 is equal to 40. As the winal unit resets after only counting to 18, the Long Count consistently uses base-20 only if the tun is considered the primary unit of measurement, not the k'in; with the k'in and winal units being the number of days in the tun. The Long Count 0.0.1.0.0 represents 360 days, rather than the 400 in a purely base-20 (vigesimal) count.

There are also four rarely used higher-order cycles: piktun, kalabtun, k'inchiltun, and alautun.

Since the Long Count dates are unambiguous, the Long Count was particularly well suited to use on monuments. The monumental inscriptions would not only include the 5 digits of the Long Count, but would also include the two tzolk'in characters followed by the two haab' characters.

Misinterpretation of the Mesoamerican Long Count calendar is the basis for a popular belief (bullshit) that a cataclysm will take place on December 21, 2012. December 21, 2012 is simply the day that the calendar will go to the next b'ak'tun, at Long Count 13.0.0.0.0. The date on which the calendar will go to the next piktun (a complete series of 20 b'ak'tuns), at Long Count 1.0.0.0.0.0, will be on October 13, 4772.

Sandra Noble, executive director of the Mesoamerican research organization Foundation for the Advancement of Mesoamerican Studies, Inc. (FAMSI), notes that "for the ancient Maya, it was a huge celebration to make it to the end of a whole cycle". She considers the portrayal of December 2012 as a doomsday or cosmic-shift event to be "a complete fabrication and a chance for a lot of people to cash in."

Table of Long Count units

Days	Long Count period	Long Count unit	Approximate Solar Years
1		1 K'in
20	20 K'in	1 Winal
360	18 Winal	1 Tun	1
7,200	20 Tun	1 K'atun	20
144,000	20 K'atun	1 B'ak'tun	394
2,880,000	20 B'ak'tun	1 Piktun	7,885
57,600,000	20 Piktun	1 Kalabtun	157,704
1,152,000,000	20 Kalabtun	1 K'inchiltun	3,154,071
23,040,000,000	20 K'inchiltun	1 Alautun	63,081,429

Supplementary Series

Many Classic period inscriptions include a series of glyphs known as the Supplementary Series. The operation of this series was largely worked out by John E. Teeple (1874–1931). The Supplementary Series most commonly consists of the following elements:

Lords of the Night

Main article: Lords of the Night

Each night was ruled by one of the nine lords of the underworld. This nine day-cycle was usually written as two glyphs: a glyph that referred to the Nine Lords as a group, followed by a glyph for the lord that would rule the next night.

Lunar Series

A lunar Series generally is written as five glyphs that provide information about the current lunation, the number of the lunation in a series of six, the current ruling lunar deity and the length of the current lunation.

Moon age

The Maya counted the number of days in the current lunation. They used two systems for the zero date of the lunar cycle: either the first night they could see the thin crescent moon or the first morning when they could not see the waning moon. The age of the moon was depicted by a set of glyphs that mayanists coined glyphs D and E:

• A new moon glyph was used for day zero in the lunar cycle.

• D glyphs were used for lunar ages for days 1 through 19, with the number of days that had passed from the new moon accompanied by a glyph that resembled a hand.

• For lunar ages 20 to 30, an E glyph was used, with the number of days from 20.

Lunation number and lunar deity

The Maya counted the lunation in a cycle of six, numbered zero through 5. Each one was ruled by one of the six Lunar Deities. This was written as two glyphs: a glyph for the completed lunation in the lunar count with a coefficient of 0 through 5 and a glyph for the lunar deity that ruled the current lunation. Teeple found that Quirigua Stela E (9.17.0.0.0) is lunar deity 2 and that most other inscriptions use this same moon number. It is an interesting date because it was a k'atun completion and a solar eclipse was visible in the Maya area two days later on the first unlucky day of Wayeb'.

Lunation length

The length of the lunar month is 29.53059 days so if you count the number of days in a lunation it will be either 29 or 30 days. The maya wrote whether the lunar month was 29 or 30 days as two glyphs: a glyph for lunation length followed by either a glyph made up of a moon glyph over a bundle with a suffix of 19 for a 29 day lunation or a moon glyph with a suffix of 10 for a 30 day lunation.

Short Count

In the kingdoms of Postclassic Yucatán, the linear Long Count notation fell into disuse and gave way to a cyclical Short Count of 13 k'atuns (or 260 tuns), in which each k'atun was named after its concluding day, Ahau ('Lord'). 1 Imix was selected as the recurrent 'first day' of the cycle, corresponding to 1 Cipactli in the Aztec day count. The cycle was counted from katun 11 Ahau to katun 13 Ahau, with the coefficients of the katuns' concluding days running in the order 11 – 9 – 7 – 5 – 3 – 1 – 12 – 10 – 8 – 6 – 4 – 2 – 13 Ahau (since a division of 20 × 360 days by 13 falls 2 days short). The concluding day 13 Ahau was followed by the re-entering first day 1 Imix. This is the system as found in the colonial Books of Chilam Balam. In characteristic Mesoamerican fashion, these books project the cycle onto the landscape, with 13 Ahauob 'Lordships' dividing the land of Yucatán into 13 'kingdoms'.

Venus cycle

Another important calendar for the Maya was the Venus cycle. The Maya kings had skilled astronomers who could calculate the Venus cycle with great accuracy. There are six pages in the Postclassic Dresden Codex devoted to the accurate calculation of the heliacal rising of Venus. The Maya were able to achieve such accuracy by careful observation over many years. Venus was often referred to as both "The Morning Star" and "The Evening Star" because of its visibility during both times. This makes Venus unique. There are various theories as to why the Venus cycle was especially important for the Maya. Across Mesoamerica, Venus was often depicted as "defeating" the Sun and the Moon, perhaps because of its persistent visibility after transitions from day-into-night (and vice-versa). Most scholars agree that Venus was associated with war and that the Maya used it to divine good times (called electional astrology) for their coronations and wars. Maya rulers planned for wars to begin when Venus rose.

See also

• Maya religion
• Tres Zapotes Stela C
• Mayanism
• Lunar calendar
• 2012 phenomenon

References

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Roys, Ralph L. (1967). The Book of Chilam Balam of Chumayel. Norman: University of Oklahoma Press. {{cite book}}: templatestyles stripmarker in |author= at position 1 (help)CS1 maint: numeric names: authors list (link)

Schele, Linda (1992). A Forest of Kings: The Untold Story of the Ancient Maya (originally published New York: Morrow © 1990, pbk reprint ed.). New York: Harper Perennial. ISBN 0-688-11204-8. OCLC 145324300. {{cite book}}: Unknown parameter |coauthors= ignored (|author= suggested) (help); templatestyles stripmarker in |author= at position 1 (help); templatestyles stripmarker in |coauthors= at position 5 (help)CS1 maint: numeric names: authors list (link)

Tedlock, Barbara (1992 rev. ed.). Time and the Highland Maya. Albuquerque: University of New Mexico Press. ISBN 0-8263-0577-6. OCLC 7653289. {{cite book}}: Check date values in: |year= (help); templatestyles stripmarker in |author= at position 1 (help)CS1 maint: numeric names: authors list (link) CS1 maint: year (link)

Tedlock, Dennis notes, trans., ed. (1985). Popol Vuh: The Definitive Edition of the Mayan Book of the Dawn of Life and the Glories of Gods and Kings. with commentary based on the ancient knowledge of the modern Quiché Maya. New York: Simon & Schuster. ISBN 0-671-45241-X. OCLC 11467786. {{cite book}}: templatestyles stripmarker in |editor= at position 1 (help)CS1 maint: multiple names: editors list (link) CS1 maint: numeric names: editors list (link)

Thomas, Cyrus (1897). "Day Symbols of the Maya Year". In J. W. Powell (ed.) (ed.). Sixteenth Annual Report of the Bureau of American Ethnology to the Secretary of the Smithsonian Institution, 1894–1895. Washington DC: Bureau of American Ethnology, Smithsonian Institution; U.S. Government Printing Office. pp. 199–266. OCLC 14963920. {{cite book}}: |editor= has generic name (help); |format= requires |url= (help); External link in |chapterurl= (help); Unknown parameter |chapterurl= ignored (|chapter-url= suggested) (help); templatestyles stripmarker in |author= at position 1 (help)CS1 maint: numeric names: authors list (link)

Thompson, J. Eric S. (1960 and subsequent printings). Maya Hieroglyphic Writing: An Introduction. Civilization of the American Indian Series, No. 56 (3rd ed.). Norman: University of Oklahoma Press. ISBN 0-8061-0447-3. OCLC 275252. {{cite book}}: Check date values in: |year= (help); templatestyles stripmarker in |author= at position 1 (help)CS1 maint: numeric names: authors list (link) CS1 maint: year (link)

Tozzer, Alfred M. notes, trans., ed. (1941). Landa's Relación de las cosas de Yucatán: a translation. Papers of the Peabody Museum of American Archaeology and Ethnology, Harvard University vol. 18. Charles P. Bowditch and Ralph L. Roys (additional trans.) (translation of Diego de Landa's Relación de las cosas de Yucatán [orig. ca. 1566], with notes, commentary, and appendices incorporating translated excerpts of works by Gaspar Antonio Chi, Tomás López Medel, Francisco Cervantes de Salazar, and Antonio de Herrera y Tordesillas. English ed.). Cambridge, MA: Peabody Museum of Archaeology and Ethnology. OCLC 625693. {{cite book}}: templatestyles stripmarker in |editor= at position 1 (help)CS1 maint: multiple names: editors list (link) CS1 maint: numeric names: editors list (link)

Voss, Alexander (2006). "Astronomy and Mathematics". In Nikolai Grube (ed.) (ed.). Maya: Divine Kings of the Rain Forest. Eva Eggebrecht and Matthias Seidel (assistant eds.). Cologne, Germany: Könemann. pp. 130–143. ISBN 978-3-8331-1957-6. OCLC 71165439. {{cite book}}: |editor= has generic name (help); templatestyles stripmarker in |author= at position 1 (help)CS1 maint: numeric names: authors list (link)

External links

• Day Symbols of the Maya Year at Project Gutenberg 1897 text by Cyrus Thomas
• Interactive Maya Calendars
• Maya Calendar and Links on diagnosis2012.co.uk (The calculator uses the proleptic Gregorian calendar, with a number of links to other Maya calendar sites.)
• Maya Calendar, Date conversions, contemporary year version, Tzolkin and Haab day in Calendar Rounds
• Maya Cycles of Time at Convergence
• The Long Count Mayan Calendar System by Keith M. Hunter author of "The Lost Age of High Knowledge" 2011
• Today's Long Count
• Understanding Mayan Calendar with animation