Enter a Gregorian date to convert it to the Mayan Long Count.
Long Count Date
13.0.0.0.0
1,872,000 days since creation
Notable Long Count Dates
Long Count
Gregorian Date
Significance
0.0.0.0.0
Aug 11, 3114 BC
Creation date (mythological)
7.0.0.0.0
Feb 11, 354 BC
Classic Maya beginnings
9.0.0.0.0
Dec 11, 435 AD
Early Classic period
10.0.0.0.0
Mar 13, 830 AD
Terminal Classic collapse
13.0.0.0.0
Dec 21, 2012
Great Cycle completion
How to Use the Mayan Calendar Converter
To use the Mayan Long Count Calendar Converter, enter the Long Count values for Baktun, Katun, Tun, Winal, and Kin. The converter will instantly display the corresponding Gregorian date, Julian Day Number, and total days elapsed since the Mayan creation date. For reverse conversion, enter a Gregorian date to find its Mayan Long Count equivalent.
What the Result Means
The result of the conversion shows the Gregorian date corresponding to the entered Mayan Long Count. This allows you to understand the historical significance of specific Mayan dates in the context of the Gregorian calendar.
Formula and Logic
The Mayan Long Count is based on a base-20 number system. The formula to convert a Mayan Long Count to a Gregorian date is: JDN = Baktun * 144,000 + Katun * 7,200 + Tun * 360 + Winal * 20 + Kin + 584,283. The GMT correlation constant (584,283) maps the Mayan Long Count onto the Julian Day Number framework used by modern astronomers.
Practical Tips and Limitations
Ensure accurate input of the Long Count values to get the correct Gregorian date. The converter assumes the GMT correlation constant is 584,283. Be aware that the Mayan calendar system is cyclical, and the completion of a 13-Baktun cycle does not indicate the end of the world as popularized in media.
Frequently Asked Questions
What is the Long Count? The Long Count is a Mayan calendar system that tracks time in cycles of 20, 400, 8,000, 160,000, and 3,200,000 days, starting from a mythical creation date. What is the GMT correlation? The GMT correlation constant (584,283) is used to map the Mayan Long Count onto the Julian Day Number framework used by modern astronomers. What happened on 13.0.0.0 in December 2012? On December 21, 2012, the Long Count reached 13.0.0.0, completing a cycle of exactly 13 Baktuns. This was significant in Mayan cosmology but did not indicate the end of the world as popularized in media. How does the base-20 number system work? The Mayan Long Count uses a base-20 number system, where each unit is 20 times the unit below it. For example, a Winal is 20 Kin, a Tun is 20 Winals, and so on. How do Tzolkin and Haab relate to the Long Count? The Tzolkin and Haab are two other calendars used by the Maya alongside the Long Count. The Tzolkin is a 20-day cycle, and the Haab is a 365-day cycle. Together, they provide a more comprehensive timekeeping system.
Frequently Asked Questions
The Long Count is a Mayan calendar system that tracks time in cycles of 20, 400, 8,000, 160,000, and 3,200,000 days, starting from a mythical creation date.
The GMT correlation constant (584,283) is used to map the Mayan Long Count onto the Julian Day Number framework used by modern astronomers.
On December 21, 2012, the Long Count reached 13.0.0.0, completing a cycle of exactly 13 Baktuns. This was significant in Mayan cosmology but did not indicate the end of the world as popularized in media.
The Mayan Long Count uses a base-20 number system, where each unit is 20 times the unit below it. For example, a Winal is 20 Kin, a Tun is 20 Winals, and so on.
The Tzolkin and Haab are two other calendars used by the Maya alongside the Long Count. The Tzolkin is a 20-day cycle, and the Haab is a 365-day cycle. Together, they provide a more comprehensive timekeeping system.
Convert any Mayan Long Count date to its Gregorian equivalent — or reverse — using the GMT 584283 correlation constant. This tool performs the three-step arithmetic (day-count summation, Julian Day Number derivation, and JDN-to-Gregorian conversion) that scholars have used since Joseph Goodman formalized the correlation in 1905.
How the Mayan Long Count Calendar Works
The Long Count is a linear, non-repeating count of days elapsed since the mythological creation date of 4 Ajaw 8 Kumk'u. Unlike the familiar 365-day Haab' or the 260-day Tzolk'in — both cyclical, both repeating — the Long Count accumulates days without ever resetting, making it the only Mayan calendar system capable of specifying a unique historical date. That property is exactly why archaeologists rely on it to anchor Mesoamerican events to the Gregorian timeline.
The vigesimal (base-20) counting system
The Maya counted in base-20 (vigesimal), and the Long Count reflects that architecture at most levels. Positions increase by a factor of 20 moving left — with one deliberate exception at the third position, where the tun uses 18 uinals rather than 20. That break from strict base-20 gives the tun 360 days, a close approximation to the solar year and a practical anchor for agricultural and ceremonial scheduling.
The five positional glyphs: baktun, katun, tun, uinal, kin
A Long Count date is written in five positions separated by dots: baktun.katun.tun.uinal.kin — for example, 9.14.6.3.1. Reading left to right, each digit represents a progressively larger time unit, the same way digits in a decimal number carry place value. Glyphs for these positions appear on stone stelae throughout the Maya lowlands and are catalogued extensively in the Dresden Codex, one of the most important surviving primary sources for Mayan calendrical knowledge.
The Mayan creation date and how Long Count dates are anchored
The anchor point for every Long Count date is 0.0.0.0.0, the Mayan creation date, which corresponds to August 11, 3114 BCE in the proleptic Gregorian calendar under GMT correlation constant 584283. Every subsequent Long Count date is the number of days accumulated since that mythological starting point. The 13th baktun cycle completed at 13.0.0.0.0, equivalent to December 21, 2012 CE — a calendrical milestone, not a terminus.
Understanding Baktun, Katun, Tun, Uinal, and Kin
Each of the five Long Count positions has a fixed day-count value. Parsing any Long Count inscription means knowing these values — or keeping the table below within reach.
Day-count equivalents for each unit
1 kin = 1 day. The kin is the base unit. 1 uinal (also spelled winal in modern orthography) = 20 kins = 20 days. Both spellings appear in peer-reviewed literature without distinction. 1 tun = 18 uinals = 360 days — not 400 days; the tun intentionally breaks the vigesimal pattern to approximate the solar year, a common point of confusion for readers familiar with Aztec calendrical systems. 1 katun = 20 tuns = 7,200 days ≈ 19.7 years.1 baktun = 20 katuns = 144,000 days ≈ 394.3 years.
Historical spans each unit covers in real-world Mesoamerican history
Classic Maya inscriptions span mostly baktuns 8 through 10, covering roughly 41 BCE to 830 CE — the period of great monument construction at Palenque, Tikal, Copán, and Quiriguá. A single katun (~19.7 years) approximates a long royal reign; many Maya rulers are commemorated on katun-ending stelae. A tun-ending (360-day anniversary) was a common occasion for dedicating smaller monuments.
How to read a Long Count inscription
Reading 9.14.6.3.1 from left to right: 9 baktuns, 14 katuns, 6 tuns, 3 uinals, 1 kin. Each digit is multiplied by the unit's day value, the products summed, and the GMT constant added to yield a Julian Day Number. The worked example below shows this arithmetic in full for 9.16.7.15.3.
Mayan Long Count Period Units at a Glance
Unit Name
Composed Of
Total Days
Approx. Gregorian Span
Notes
Kin
1 kin
1
1 day
Base unit; place value = 1
Uinal (Winal)
20 kins
20
~3 weeks
Both spellings valid in academic literature
Tun
18 uinals
360
~0.986 years
Breaks vigesimal pattern to approximate solar year
Table 1. The five standard Long Count period units plus the next higher-order unit, the piktun. The tun's 360-day value — rather than 400 — is the most frequent source of conversion errors.
The GMT Correlation Constant Explained
Any Long Count date is, on its own, a count of days relative to the Mayan creation point. Translating that count into a specific year, month, and day on the Gregorian calendar requires a bridge between the two systems: the correlation constant, which is the Julian Day Number (JDN) assigned to the Mayan creation date 0.0.0.0.0. Once that JDN is established, every other Mayan date follows by simple addition.
What a correlation constant does mathematically
The Julian Day Number is a continuous count of days used by astronomers, anchored to January 1, 4713 BCE (Julian calendar). If the Mayan creation date 0.0.0.0.0 equals JDN 584,283, then a Long Count date with a total day count of D corresponds to JDN 584,283 + D, convertible to a calendar date by standard algorithms. The correlation constant acts as a fixed offset linking two independent counting systems.
The GMT constant: Goodman, Martínez, and Thompson
GMT 584283 was established through the independent work of three scholars: Joseph T. Goodman in 1905, Juan Martínez Hernández in 1926, and J. Eric S. Thompson in 1927 — hence the initials GMT. Thompson published a revised figure of 584285 in his 1950 monograph, and a further variant of 584286 appears in portions of the literature. The differences between these constants are small (one to three days) but consequential enough to require citation when publishing converted dates.
The ±1-day uncertainty window and alternative constants
Floyd Lounsbury's 1983 astronomical verification cross-checked Venus synodic cycles recorded in the Dresden Codex against known Gregorian dates, providing independent support for the 584283 figure. Anthony Aveni's Skywatchers of Ancient Mexico situates this correlation within broader archaeoastronomical evidence, documenting why the GMT family of constants holds scholarly consensus. A ±1-day uncertainty window still persists: any date converted with this tool may be off by one day depending on which peer-reviewed source is treated as authoritative.
Why this tool uses 584283
This calculator defaults to GMT 584283 because it is the original, most widely cited correlation and the baseline against which all variants are measured. The formula is: Gregorian date = JDN of 0.0.0.0.0 (584,283) + total day count of the Long Count date. Researchers who need to verify results against Thompson's 1950 revision can add 2 to every JDN output; those using the Modified Thompson constant add 3.
Comparison of Mayan Calendar Correlation Constants
Constant
JDN Value
Creation Date (Gregorian)
Key Proponent
Date Shift vs GMT 584283
Goodman–Martínez–Thompson (GMT)
584,283
August 11, 3114 BCE
Goodman (1905), Martínez (1926), Thompson (1927)
Baseline (0 days)
Thompson Revised
584,285
August 13, 3114 BCE
Thompson (1950)
+2 days
Modified Thompson
584,286
August 14, 3114 BCE
Various 20th-century revisions
+3 days
Lounsbury Astronomical Verification
584,283
August 11, 3114 BCE
Lounsbury (1983), via Dresden Codex Venus tables
0 days (confirms GMT)
Table 2. The four principal correlation constants. All converted dates should cite which constant was used. For 9.16.7.15.3, GMT 584283 yields January 28, 759 CE; Thompson Revised 584285 yields January 30, 759 CE.
Converting Mayan Long Count Dates to Gregorian Calendar
The conversion procedure has three distinct steps. Understanding each step makes it possible to verify the calculator's output manually and to spot errors in secondary sources that may have applied the wrong constant or the wrong calendar system.
Step 1 — Convert the Long Count to a total day count
Multiply each positional digit by its corresponding day value and sum the results:
Total Days = (baktun × 144,000) + (katun × 7,200) + (tun × 360) + (uinal × 20) + kin
This gives the number of days elapsed since the Mayan creation date 0.0.0.0.0.
Step 2 — Add the GMT correlation constant to get a Julian Day Number
Add 584,283 to the total day count:
Julian Day Number (JDN) = Total Days + 584,283
The result is a JDN on the continuous astronomical day count, cross-checkable with any standard JDN reference or with the Julian Day Number calculator on this site.
Step 3 — Convert the Julian Day Number to a Gregorian calendar date
JDN-to-Gregorian conversion follows the algorithm published by Fliegel and Van Flandern in the Journal of the British Astronomical Association (1968). This closed-form, integer-arithmetic procedure handles leap years, the Gregorian reform of 1582, and BCE dates correctly. Dates before October 15, 1582 CE are expressed in the proleptic Gregorian calendar — Gregorian rules projected backward before the reform — for consistency across the full Long Count range.
Reverse conversion: Gregorian to Long Count
The reverse process subtracts 584,283 from the Gregorian date's JDN to recover total elapsed days, then decomposes that number using successive integer division: divide by 144,000 to extract the baktun count, the remainder by 7,200 for katuns, and so on through tuns, uinals, and kins. You can also measure the span between two converted dates using the date difference calculator once both Long Count values have been translated to Gregorian. Dates before the creation date (0.0.0.0.0) yield negative total-day values and require careful sign handling in the decomposition step.
Worked Example: Converting Mayan Long Count 9.16.7.15.3
The following example shows every arithmetic step from Long Count notation to a specific Gregorian date. The values match the calculator's output exactly; replicate them by entering 9, 16, 7, 15, 3 into the respective baktun-through-kin fields.
Input
Mayan Long Count date: 9.16.7.15.3 (baktun = 9, katun = 16, tun = 7, uinal = 15, kin = 3)
Correlation constant
GMT 584,283
Computing total elapsed days
Multiply each position by its day value:
9 × 144,000 = 1,296,000
16 × 7,200 = 115,200
7 × 360 = 2,520
15 × 20 = 300
3 × 1 = 3
Sum: 1,296,000 + 115,200 + 2,520 + 300 + 3 = 1,414,023 total days elapsed since the Mayan creation date 0.0.0.0.0.
Adding the GMT constant to get JDN
1,414,023 + 584,283 = JDN 1,998,306
JDN to Gregorian date result
Applying the Fliegel–Van Flandern JDN-to-Gregorian algorithm to JDN 1,998,306 produces January 28, 759 CE in the proleptic Gregorian calendar.
±2-day caveat: Using Thompson's revised GMT 584285 instead shifts the result to January 30, 759 CE. Any publication of this converted date should cite which constant was used.
This date falls in the Late Classic period of Maya civilization (~600–900 CE), the era of the densest surviving Long Count inscriptions at major sites including Palenque and Copán. Monument construction and dedication were at their height in the southern lowlands during the Late Classic — making a Long Count date of 9.16.7.15.3 historically plausible as a monument-dedication date from that era.
Expected output: January 28, 759 CE (proleptic Gregorian), using GMT correlation constant 584,283; JDN 1,998,306.
Historical Accuracy and the Mayan Calendar Collapse Myth
What 13.0.0.0.0 actually represented to the Maya
December 21, 2012 (Long Count 13.0.0.0.0) marked the completion of the 13th baktun cycle — roughly analogous to a car odometer rolling from 999,999 to 1,000,000. In Mayan cosmology, the rollover of a large cycle carried ceremonial significance and was almost certainly observed as a renewal point, not an endpoint. Epigraphic evidence from multiple sites shows that the Maya anticipated and planned for calendrical events beyond 13.0.0.0.0.
The 2012 phenomenon debunked
No authenticated Classic Maya inscription predicts an apocalyptic event on this date. Tortuguero Monument 6, the inscription most frequently cited by doomsday proponents, describes the expected descent of the deity Bolon Yokte' K'uh at the end of the 13th baktun — a theophany, not a destruction narrative. The Archaeological Institute of America issued an official statement in 2012 noting that Maya scholars unanimously rejected the doomsday interpretation as having no basis in the textual or archaeological record. Higher-order cycles beyond the baktun — the piktun (20 baktuns = 2,880,000 days), the kalabtun, and still larger units — demonstrate that the calendar was designed to continue indefinitely.
Ongoing use of the Mayan calendar by contemporary Maya communities
Contemporary K'iche' and Yucatec Maya communities have maintained unbroken use of the 260-day Tzolk'in calendar alongside the Gregorian calendar. Day-keepers (ajq'ijab') continue to track Tzolk'in cycles for agricultural, ceremonial, and ritual scheduling. This living continuity is one reason scholars treat colonial-era Maya documentary records as valuable cross-references when debating correlation constants — the calendar tradition never truly went dark.
Common Mistakes When Converting Mayan Dates
Confusing the tun with a 400-day period
The tun is 360 days, not 365 or 400. The 400-day period appears in Mesoamerican contexts but belongs to a different counting tradition sometimes conflated with Aztec or other Central Mexican calendar structures. Using 400 instead of 360 for the tun inflates every converted date by 40 days per tun position — a systematic error that compounds rapidly across multi-tun spans.
Mixing up Julian and Gregorian calendar outputs
Dates before October 15, 1582 CE must be expressed in the proleptic Gregorian calendar for cross-era consistency. Failing to apply this distinction creates systematic errors of 10 to 13 days, depending on the century. Some older Mesoamerican scholarship reports converted dates in the Julian calendar without labeling them clearly — always check the source's calendar convention before comparing two converted dates.
Using the wrong correlation constant without noting it
Always specify which correlation constant you used when publishing a converted date. GMT 584283, Thompson 584285, and Modified Thompson 584286 produce different Gregorian dates by up to three days for any given Long Count input. Omitting this citation makes the result unreproducible and impossible to reconcile with other published conversions.
Off-by-one errors in positional notation
Long Count notation 9.0.0.0.0 is not the number 9 — it represents 9 baktuns = 1,296,000 days. Some secondary sources write Long Count dates with only four positions, dropping a leading zero or, in rare cases, the baktun entirely when it equals zero. This truncation can cause confusion for dates near the creation epoch and should be treated with caution in any automated parsing pipeline.
Major Mayan Long Count Dates Mapped to the Gregorian Timeline
Long Count Date
Gregorian Equivalent
Event / Significance
0.0.0.0.0
August 11, 3114 BCE
Mayan mythological creation date (GMT 584283)
7.16.3.2.13
~32 BCE
Approximate date of earliest known Long Count inscription (Stela 2, Chiapa de Corzo)
9.10.0.0.0
January 24, 633 CE
Peak of Classic Maya monument construction
9.16.7.15.3
January 28, 759 CE
Worked example date; Late Classic period
13.0.0.0.0
December 21, 2012 CE
13th baktun cycle completion; no apocalyptic significance
14.0.0.0.0
March 26, 2407 CE
14th baktun begins; calendar continues
Figure 1. Selected Long Count milestones on the Gregorian timeline, from the mythological creation date in 3114 BCE through the start of the 14th baktun in 2407 CE. All dates use GMT 584283.
FAQ: Mayan Calendar Conversions
What is the GMT correlation constant and why does it matter?
The GMT constant (584,283) is the Julian Day Number assigned to the Mayan creation date 0.0.0.0.0, linking the Mayan day-count to the absolute Gregorian timeline. Without it, a Long Count date is merely a relative count of days with no fixed position in history. The constant was established through the work of Joseph T. Goodman (1905), Juan Martínez Hernández (1926), and J. Eric S. Thompson (1927), and independently verified by Floyd Lounsbury in 1983 using Venus synodic cycle data recorded in the Dresden Codex. Any converted date is only as reliable as the correlation constant applied, which is why published conversions should always cite which value was used.
Did the Mayan calendar really end on December 21, 2012?
No. December 21, 2012 (Long Count 13.0.0.0.0) marked the completion of the 13th baktun cycle — analogous to a car odometer rolling from 99,999 to 100,000 miles. No authenticated Maya inscription predicts an apocalyptic event on this date; the most-cited inscription, Tortuguero Monument 6, describes the arrival of a deity, not destruction. The Maya calendar includes higher-order cycles — the piktun (20 baktuns = 2,880,000 days), the kalabtun, and beyond — demonstrating the calendar was designed to extend millions of years into the future. Contemporary K'iche' Maya communities observed the baktun rollover as a ceremonial renewal, consistent with how the Maya historically marked major cycle completions.
How do you convert a Mayan Long Count date to Gregorian?
Multiply each positional digit by its day-count value (baktun × 144,000; katun × 7,200; tun × 360; uinal × 20; kin × 1), then sum all five products to get total elapsed days. Add the GMT constant 584,283 to obtain a Julian Day Number. Finally, apply the Fliegel–Van Flandern JDN-to-Gregorian algorithm to convert the JDN to a calendar date. For dates before October 15, 1582 CE, the result is expressed in the proleptic Gregorian calendar. The calculator on this page performs all three steps automatically and displays the result with a ±1-day uncertainty note.
What do baktun, katun, tun, uinal, and kin mean?
They are the five positional units of the Long Count, each representing a fixed number of days: kin = 1 day, uinal = 20 days, tun = 360 days, katun = 7,200 days (~19.7 years), and baktun = 144,000 days (~394.3 years). The tun is the only unit that breaks the otherwise vigesimal (base-20) pattern — it uses 18 uinals rather than 20 to approximate the solar year, which is the most common source of manual calculation errors. A Long Count date is written as baktun.katun.tun.uinal.kin, for example 9.16.7.15.3.
Why are there different Mayan calendar correlation constants?
The Maya recorded dates on perishable bark-paper codices, the vast majority of which were destroyed during the Spanish conquest of the 16th century. Oral calendar traditions continued among indigenous communities but accumulated small uncertainties over generations. Scholars derived correlation constants by cross-referencing surviving stone inscriptions with independently datable astronomical events — especially Venus synodic cycles — and with colonial-era Spanish–Maya documentary records. Different data sets and weighting schemes yield slightly different JDN values, which is why GMT 584283, Thompson 584285, and Modified Thompson 584286 all appear in the scholarly literature.
Can you convert Gregorian dates back to Mayan Long Count?
Yes. Calculate the Gregorian date's Julian Day Number, subtract 584,283 to get the total days elapsed since the Mayan creation date, then decompose that number using successive integer division: divide by 144,000 for the baktun count, the remainder by 7,200 for katuns, then by 360 for tuns, by 20 for uinals, and the final remainder is the kin count. The reverse-conversion input on this calculator performs this automatically. Negative results — for Gregorian dates before August 11, 3114 BCE — indicate dates prior to the Mayan creation epoch and are rarely encountered outside theoretical chronology.
What is the current date in the Mayan Long Count system?
The current Long Count date changes daily and is best determined by entering today's Gregorian date into the reverse-conversion input above. As of early 2025, the Long Count is in the 14th baktun, which began at 13.0.0.0.1 on December 22, 2012 CE. The precise notation for any given day depends on the elapsed time since that point; the calculator computes it exactly. The 14th baktun will not complete until approximately March 26, 2407 CE, so the current era of the Long Count has several centuries remaining.
Related Calendar Tools and Converters
Mayan Long Count conversion relies on Julian Day Numbers as an intermediate step — the underlying mechanism is explained in detail on the Julian Day Number calculator page, which also lets you verify any JDN value independently. To measure the span between two converted Long Count dates in years, months, and days, the date difference calculator accepts standard Gregorian inputs for exactly that purpose. Researchers studying comparative historical calendars will find parallel tools for the Hebrew and Islamic Hijri systems in the related calculators below.
