Mayan Calendar Converter (Long Count, Tzolk’in & Haab’ from a date)

Understanding the Maya calendar converter — concept and principle

This converter turns a Gregorian date into the Maya Long Count, the 260-day Tzolk'in and the 365-day Haab', and gives the day count since the start of the current era. It is used by students of Mesoamerican history, museum visitors, writers and anyone curious about the Maya calendar.

How it is calculated

1. Julian Day Number (JDN) of the date.
2. Days since 13.0.0.0.0: k = JDN − 584,283 (the Goodman–Martínez–Thompson, or GMT, correlation; 584,285 is an alternative).
3. Long Count: k split into bak'tun (144,000 days), k'atun (7,200), tun (360), winal (20) and k'in (1).
4. Tzolk'in: number = (k + 3) mod 13 + 1; day name = name number (k + 19) mod 20 of the 20 names (Imix … Ajaw).
5. Haab': position (k + 348) mod 365 in 18 months of 20 days plus the 5-day Wayeb.

The principle

The Maya used several interlocking cycles. The Long Count is a place-value day count, mostly base 20, from a mythical starting point, 13.0.0.0.0, which fell on 4 Ajaw 8 Kumk'u. The Tzolk'in pairs 13 numbers with 20 day names, giving 260 combinations. The Haab' is a 365-day year of 18 named months of 20 days plus 5 extra days. The correlation constant links the Maya count to the Julian Day Number used by astronomers; GMT is the most widely accepted, supported by radiocarbon dating of wooden lintels from Tikal.

Worked example

Default inputs: 10 Nov 2026, GMT correlation 584,283.

1. JDN = 2,461,355; k = 2,461,355 − 584,283 = 1,877,072 days.
2. 1,877,072 = 13 × 144,000 + 0 × 7,200 + 14 × 360 + 1 × 20 + 12, so the Long Count is 13.0.14.1.12.
3. Tzolk'in: (1,877,072 + 3) mod 13 + 1 = 6; name number (k + 19) mod 20 = 11 → 6 Eb.
4. Haab': (k + 348) mod 365 = 225 = 11 × 20 + 5 → 5 Keh.

How to read the result

The Long Count passed 13.0.0.0.0 on 21 December 2012 (GMT), the date popularly linked to "the end of the world"; for the Maya it simply began a new bak'tun cycle. Using 584,285 shifts every date by two days, so state which correlation you used when sharing results.

Common mistakes

• Mixing correlation constants between sources.
• Expecting dates before the start of the current Long Count to work here.
• Confusing the Julian calendar with the Julian Day Number.
• Using local time near midnight, which can shift the day.

Frequently asked questions

What is today's Maya Long Count?

For 10 Nov 2026 with the GMT correlation, 13.0.14.1.12, 6 Eb 5 Keh.

What happened on 21 December 2012?

The Long Count reached 13.0.0.0.0 again, the end of a bak'tun cycle, not the end of the world.

What is the GMT correlation?

The constant 584,283 linking the Maya day count to the Julian Day Number, the most widely used value.

Sources: D. J. Kennett et al. (2013), "Correlating the Ancient Maya and Modern European Calendars with High-Precision AMS 14C Dating", Scientific Reports 3:1597