Mayan Long Count Calendar Converter

Convert Mayan Long Count dates to Gregorian calendar dates using the GMT correlation constant.

Long Count → Gregorian

13.0.0.0.0
Gregorian Date
December 21, 2012
Julian Day Number: 2,456,283
Total Days Elapsed
1,872,000
Days from Today
0

Gregorian → Long Count

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 CountGregorian DateSignificance
0.0.0.0.0Aug 11, 3114 BCCreation date (mythological)
7.0.0.0.0Feb 11, 354 BCClassic Maya beginnings
9.0.0.0.0Dec 11, 435 ADEarly Classic period
10.0.0.0.0Mar 13, 830 ADTerminal Classic collapse
13.0.0.0.0Dec 21, 2012Great Cycle completion

How to Use the Mayan Calendar Converter

  1. Enter the Long Count — input values for Baktun (0-19), Katun (0-19), Tun (0-19), Winal (0-17), and Kin (0-19).
  2. Read the Gregorian date — the converter instantly shows the corresponding Gregorian calendar date, Julian Day Number, and total days elapsed since the Mayan creation date.
  3. Use the reverse converter — enter any Gregorian date in the second section to find its Mayan Long Count equivalent.
  4. Compare notable dates — the reference table shows historically significant Long Count dates with their Gregorian equivalents.

Understanding the Mayan Calendar System

The ancient Maya developed one of the most sophisticated calendar systems in human history, rivaling and in some respects surpassing the astronomical precision of contemporary Old World civilizations. Their calendar system was not a single calendar but an interlocking set of cycles — the Long Count, the Tzolkin, and the Haab — that together provided both practical timekeeping for agriculture and ritual, and a vast cosmological framework for recording history across millennia.

The Long Count: Tracking Deep Time

The Long Count was the Maya's solution to a fundamental problem in calendar design: how to uniquely identify dates across time spans longer than a human lifetime. Using a modified vigesimal (base-20) number system, it counts the total number of days elapsed since a mythological creation date — 0.0.0.0.0, corresponding to August 11, 3114 BC in the Gregorian calendar. The five-place notation encodes progressively larger time units:

JDN = Baktun×144,000 + Katun×7,200 + Tun×360 + Winal×20 + Kin + 584,283

The Kin represents a single day. Twenty Kins make a Winal (20 days). Eighteen Winals make a Tun (360 days, approximating a solar year). Twenty Tuns make a Katun (7,200 days, roughly 19.7 years). Twenty Katuns make a Baktun (144,000 days, roughly 394.3 years). The creation date serves as the epoch, and the GMT correlation constant (584,283) maps this system onto the Julian Day Number framework used by modern astronomers.

The 2012 Phenomenon and the Great Cycle

On December 21, 2012, the Long Count reached 13.0.0.0.0, completing a cycle of exactly 13 Baktuns (1,872,000 days, or approximately 5,125 solar years). Popular media widely mischaracterized this as a Mayan prediction of the apocalypse, but there is no evidence for such a belief in any ancient Maya text. The completion of a 13-Baktun cycle was significant in Mayan cosmology — it represented the end of one creation era and the beginning of another — but the Long Count simply continued incrementing. The Maya themselves recorded dates beyond 13.0.0.0.0, including dates millions of years in the future inscribed at the site of Palenque, demonstrating that they viewed time as infinite, not ending at any particular cycle completion.

The GMT Correlation Constant

The Goodman-Martinez-Thompson (GMT) correlation is the critical bridge between the Mayan Long Count and the Western calendar. Establishing this correlation was one of the great achievements of Mesoamerican epigraphy. Joseph Goodman first proposed a correlation in 1905, which was later refined by Juan Martinez Hernandez and J. Eric S. Thompson. The accepted value of 584,283 is supported by astronomical observations recorded in Maya inscriptions (particularly eclipse records at Palenque and Dresden Codex Venus tables), radiocarbon dates from carved wooden lintels at Tikal, and ethnohistorical records from the Spanish colonial period documenting the continuation of Maya calendar traditions.

Tzolkin and Haab: The Calendar Round

Alongside the Long Count, the Maya used two shorter cycles for daily and ceremonial timekeeping. The Tzolkin (Sacred Round) combines 13 numbers with 20 named days to produce a 260-day cycle, possibly based on the human gestation period or agricultural cycles. The Haab (Vague Year) is a 365-day solar calendar with 18 months of 20 days plus 5 "nameless days" (Wayeb) considered unlucky. Together, the Tzolkin and Haab form the Calendar Round, which uniquely identifies dates within a period of 52 Haab years (18,980 days). The Long Count was invented specifically to overcome this 52-year limitation and provide unique identifiers for dates across the full span of Maya recorded history.

Archaeological Evidence and Modern Understanding

Long Count dates appear on hundreds of Maya monuments, stelae, and architectural inscriptions. The earliest known Long Count date — 7.16.3.2.13 — appears on Stela 2 at Chiapa de Corzo, dating to 36 BC. The most famous Long Count inscriptions come from the Classic period sites of Tikal, Palenque, Copan, and Calakmul, where rulers commemorated accession dates, military victories, and ritual events with precisely dated Long Count texts. The decipherment of these inscriptions, combined with the GMT correlation, has allowed archaeologists to construct detailed political histories of Maya kingdoms with a precision rivaling medieval European chronicles.

Frequently Asked Questions

The Long Count is a calendar system used by the ancient Maya to track long periods of time. It counts days since a mythological creation date (August 11, 3114 BC). Dates use five place values: Baktun (144,000 days), Katun (7,200), Tun (360), Winal (20), and Kin (1). For example, 9.15.6.14.6 represents a specific day in Maya history.
The GMT (Goodman-Martinez-Thompson) correlation constant of 584,283 converts between the Mayan Long Count and the Julian Day Number system. It was established through astronomical records in Maya inscriptions, radiocarbon dating, and Spanish colonial ethnohistory. It means the creation date 0.0.0.0.0 equals Julian Day 584,283, or August 11, 3114 BC.
On December 21, 2012, the Long Count completed a 13-Baktun cycle (approximately 5,125 years). This was misinterpreted as a doomsday prediction, but the Maya viewed it as one cycle ending and another beginning — like an odometer rolling over. No ancient text predicts apocalypse. The count simply continued to 13.0.0.0.1 and beyond.
The Maya used vigesimal (base-20) counting with dots (1), bars (5), and a shell (0). The Long Count modifies this at the Tun level: 18 Winals (not 20) make 1 Tun (360 days), approximating a solar year. Above the Tun, it returns to base-20: 20 Tuns = 1 Katun, 20 Katuns = 1 Baktun.
The Tzolkin (260-day sacred cycle) and Haab (365-day solar calendar) combine to form the Calendar Round, which repeats every 52 Haab years. The Long Count was invented to overcome this 52-year limitation, uniquely identifying any date across thousands of years. All three systems ran simultaneously in ancient Maya society.