Maya Calendar (瑪雅長紀曆)

The Long Count & the Calendar Round — the Complete Machine of Maya Time

Overview

The Maya did not keep one calendar — they kept several at once, meshed together like the teeth of interlocking gears, and reading a date meant reading all of them. askTIAN's Tzolkʼin endpoint already gives the 260-day sacred count; this endpoint completes the machine. From any Gregorian date it computes the Long Count — the great linear day-count the Maya carved on their monuments, written as five place-values (bakʼtun.kʼatun.tun.winal.kʼin) counting the days since their creation epoch; the Haabʼ, the 365-day 'vague year' of eighteen twenty-day months plus five nameless days; the Calendar Round, the 52-year cycle in which a Tzolkʼin day and a Haabʼ day return to the same pairing; the Lord of the Night, a nine-day cycle of underworld deities; the Year Bearer that names each Haabʼ year; and the rare 819-day count. It is the difference between knowing your Maya day-sign and knowing your full Maya date — the way a Classic-period scribe at Palenque or Tikal would have inscribed it in stone.

Origin & history

The Long Count is the Maya's monumental contribution to world calendrics: a continuous tally of days from a mythological zero point, 4 Ahau 8 Cumku, which falls on 11 August 3114 BCE in the proleptic Gregorian calendar. Unlike a repeating cycle, it could name any day uniquely across millennia, and the Maya used it to anchor dynastic history with a precision unmatched in the ancient Americas. Its arithmetic is almost pure base-20 — twenty kʼin (days) to a winal, twenty tun to a kʼatun, twenty kʼatun to a bakʼtun — with a single deliberate exception: only eighteen winal make a tun, so a tun is 360 days, close to a solar year. The Haabʼ and the 260-day Tzolkʼin are older still, shared across Mesoamerica, and their meshing into the 52-year Calendar Round was the everyday dating system of Maya, Aztec and Zapotec alike.

The Long Count flourished in the Classic period (c. 250–900 CE), when cities like Tikal, Copán and Palenque raised dated stelae recording births, accessions, wars and the deaths of kings. The accession of Kʼinich Janaabʼ Pakal of Palenque — Long Count 9.9.2.4.8, 5 Lamat 1 Mol, our 27 July 615 CE — is among the best-documented dates in Maya history. After the Classic collapse the Long Count fell out of monumental use, but the Tzolkʼin and Haabʼ continued, and Maya day-keepers in highland Guatemala have maintained the 260-day count unbroken to the present. Modern correlation work fixed the bridge between the two calendars: the Goodman–Martínez–Thompson constant, Julian Day 584283, which makes the famous bakʼtun-ending 13.0.0.0.0 fall on 21 December 2012 — the date popular culture mistook for an apocalypse but which the Maya understood as the turning of a great cycle. askTIAN locks to the GMT-584283 correlation, the same one its Tzolkʼin uses, and states honestly where scholarship genuinely diverges.

How it works

Everything is pure integer arithmetic on the Julian Day Number, so the result is exact and reproducible with no ephemeris or external service. The API converts the Gregorian date to its JDN and subtracts the correlation constant 584283 to get the days elapsed since the Maya epoch. From that single number every cycle follows: the Long Count by successive division through the place-values (144000, 7200, 360, 20 — honouring the 18-winal quirk so the winal field only ever runs 0–17); the Haabʼ by an offset of 348 days that anchors the epoch to its known position of 8 Cumku, then splitting into the eighteen months and the five Wayebʼ days, given in both reformed and colonial spellings; the Tzolkʼin by the same formulas the dedicated endpoint uses, so the two always agree; the Lord of the Night by the day-count modulo nine (with the residue-zero day mapping to G9, the only one of the Nine securely identified, as Pauahtun); the Calendar Round position within the 18,980-day cycle, plus the Gregorian date on which this exact Tzolkʼin-Haabʼ pairing next recurs — your ~52-year Calendar-Round anniversary; and the Year Bearer under the Classic (Tikal/Dresden) convention seated at 0 Pop. A transparent significance score weights period-endings (tun, hotun, kʼatun and bakʼtun completions), which the Maya themselves commemorated with monuments — explicitly a measure of ceremonial weight, never personal fortune.

Good for

Use cases

Inscription Decoder

Feed a historical date and the API returns the full Long Count and Calendar Round a Classic-period scribe would have carved — ideal for museums, epigraphy teaching tools, and Maya-history apps that want to show 'this day in Maya notation'.

Calendar-Round Anniversary

The engine returns the Gregorian date on which a given day's Tzolkʼin-Haabʼ pairing next recurs, roughly 52 years later — a culturally grounded 'Maya birthday' feature distinct from the annual Gregorian one.

Today in the Long Count

Send today's date for a live readout of the current Long Count, Haabʼ month, Lord of the Night and Year Bearer — a deterministic daily widget needing no LLM, with the interpretation flag off.

Period-Ending Almanac

Because the engine flags tun, hotun, kʼatun and bakʼtun endings, an app can highlight the ceremonially weighty dates the Maya marked with stelae, and count down to the next great cycle-turn.

Key terms

Long Count
The Maya's linear day-count from the creation epoch (4 Ahau 8 Cumku, 11 Aug 3114 BCE), written in five place-values: bakʼtun.kʼatun.tun.winal.kʼin. Almost pure base-20, except that 18 winal make a tun (360 days). Uniquely names any day across millennia.
Haabʼ
The 365-day Maya 'vague year' — eighteen months of twenty days each (Pop, Woʼ, Sip … Kumkʼu) plus a five-day month of nameless, inauspicious days called Wayebʼ. Days are numbered from 0, the 'seating' (chum) of the month.
Calendar Round
The 18,980-day (52-year) cycle in which a given Tzolkʼin day and Haabʼ day return to the same pairing — the least common multiple of 260 and 365. The everyday dating system across Mesoamerica before the Long Count was needed for longer spans.
Lords of the Night
A nine-day cycle of underworld deities (Bolon Tiku), labelled G1–G9 by epigraphers because most of their names are lost; only G9 is securely identified, as Pauahtun. Computed from the day-count modulo nine.
Year Bearer
The Tzolkʼin day-sign that names a Haabʼ year, falling on the seating of Pop. Only four signs can serve as bearers; under the Classic (Tikal/Dresden) convention they are Ikʼ, Manikʼ, Eb and Kabʼan. Other traditions use different sets — a genuinely source-divergent layer.
bakʼtun
The largest commonly used Long Count unit, 144,000 days (about 394 years) — twenty kʼatun. The completion of the 13th bakʼtun on 21 December 2012 (13.0.0.0.0) closed a great cycle of 5,125 years.
GMT Correlation
The Goodman–Martínez–Thompson constant, Julian Day 584283, that bridges the Maya count and the Gregorian calendar. Alternatives (584285, 584286) shift dates by two or three days; askTIAN locks to 584283 to match its Tzolkʼin.
819-Day Count
A rarer Maya cycle of 819 days (7 × 9 × 13) tied to four directions and colours and to the god Kʼawiil. Its arithmetic is firm but its symbolism is a scholarly reconstruction, so the engine reports the station and quadrant while flagging the meaning as interpretive.

API

The askTIAN Maya Calendar API converts any date (year 100–2200, so Classic-period inscriptions work too) into the complete Maya date with pure, exact Julian-Day arithmetic on the GMT-584283 correlation — no database, no ephemeris, fully reproducible. It returns the Long Count (with the days-since-epoch and the 18-winal place-values handled correctly), the Haabʼ month and day in reformed and colonial spellings, the Tzolkʼin (always agreeing with the dedicated endpoint), the Calendar Round name and its next return date, the Lord of the Night (G1–G9), the Classic Year Bearer with its Haabʼ new-year date, the 819-day count station, and a transparent period-ending significance score, plus a fixed-section LLM reading. Honesty rails are built into the payload: the Long Count, Tzolkʼin, Haabʼ, Calendar-Round math and Lords of the Night are canonical; the correlation choice, the Year-Bearer set and the 819-count's symbolism are flagged as source-divergent; day-augury is kept out of the math. Verified to the day against 13.0.0.0.0 = 21 Dec 2012 and the Pakal inscriptions. Set interpretation:false for structured data only.

Endpoint: POST /trpc/mayan.calendar — 6 TIAN Points. See the API documentation and Playground.