Julian Date Converter
Historical Mesoamerican calendar
Mayan Date Converter
Convert Gregorian dates to Mayan Long Count, Tzolkin, and Haab values using the GMT correlation, or convert a Long Count back to Gregorian.
Live output
Result
Choose a direction, enter a Gregorian date or Mayan Long Count, and the research-model result appears here.
Guide
Mayan Date Converter for Long Count dates
This Mayan Date Converter changes Gregorian dates into Mayan Long Count values and converts Long Count input back into Gregorian dates. The result also includes the related Tzolkin and Haab cycle values produced from the same day reference.
The page uses the GMT correlation constant 584283. That is a common working correlation for Long Count conversion, but it is still an explicit scholarly assumption, so the converter labels it instead of treating every Mayan correlation proposal as interchangeable.
What this converter handles
Long Count conversion with cycle context
The converter uses Julian Day Number arithmetic as the bridge between Gregorian dates and the Mayan model. A Gregorian input is converted to JDN first, then the Long Count, Tzolkin, and Haab fields are derived from that same count.
Reverse conversion accepts the Long Count tuple only. Tzolkin and Haab values are displayed as supporting cycle context, but they are not enough by themselves to identify one absolute Gregorian date.
Gregorian to Long Count
Enter a Gregorian date and return baktun, katun, tun, uinal, and kin positions using GMT 584283.
Long Count to Gregorian
Enter a Long Count in baktun.katun.tun.uinal.kin format and recover the matching Gregorian date for this correlation.
Tzolkin and Haab output
The result includes the 260-day Tzolkin and 365-day Haab values for the converted day.
How to use it
Enter the date in the calendar you already have
Choose Gregorian to Mayan when your source is a modern Gregorian date. Choose Mayan to Gregorian only when your source is already written as a Long Count tuple.
Long Count input must use five dot-separated numbers. The converter validates the smaller positions so katun and tun stay within 0-19, uinal stays within 0-17, and kin stays within 0-19.
Use Gregorian to Mayan
Select the Gregorian direction and enter a date such as 2026-06-30 to see the Long Count and cycle values.
Use Mayan to Gregorian
Select the reverse direction and enter a value such as 13.0.13.12.19 in the Long Count field.
Check the correlation note
Use the result as a GMT-correlation conversion, not as a comparison across every proposed Mayan chronology.
Reference examples
Reference conversions from the local implementation
These examples are produced by the same local implementation used by the form. They show both the raw Long Count input syntax and the supporting cycle values returned from the same JDN.
Gregorian to Mayan
The Gregorian date 2026-06-30 converts to Long Count 13.0.13.12.19 with reference JDN 2461222.
Mayan to Gregorian
The Long Count 13.0.13.12.19 converts back to Gregorian 2026-06-30 in this GMT-correlation model.
FAQ
Mayan conversion questions
Most Mayan date conversion confusion comes from correlation choice or from mixing absolute Long Count dates with repeating cycles. These answers describe what this page actually computes.
Can I convert from Tzolkin and Haab alone?
No. Tzolkin and Haab repeat, so this page uses Long Count input for reverse conversion and reports the cycles as supporting output.
Why does the GMT correlation matter?
A correlation constant anchors Long Count day zero to a Julian Day Number. Different constants can shift the Gregorian date, so this converter states GMT 584283 directly.
Is this a Mayan ritual calendar calculator?
It is a date conversion tool. It does not interpret ritual meanings, local inscriptions, or alternative historical reconstructions.
Reference
Calendar implementation reference
The implementation follows the same arithmetic style used in standard calendrical calculation references: convert through an absolute day count, then derive the Mayan fields from that count and the stated correlation.