Convert a date
Use the calendar picker for modern CE dates, or use the dropdown fields for CE/BCE conversion. BCE uses historical year numbering: 1 BCE is followed by 1 CE, with no year zero in the input.
Maya calendrical conversion
Mesoamerican Calendar Converter
Enter a Gregorian date and convert it into the Maya Long Count, Tzolk'in, Haab', and Calendar Round. The tool runs entirely in the browser and uses the standard GMT correlation constant of 584283, matching the computation convention exposed by FAMSI's date conversion resource.
Local browser calculation
GMT 584283
No database required
Conversion result
Selected Gregorian date: ready.
Long Count
—
Baktun.Katun.Tun.Winal.K'in
Tzolk'in
—
13 numbers × 20 day signs
Haab'
—
18 months × 20 days + Wayeb'
Calendar Round
—
Tzolk'in and Haab' interlock
Lord of the Night
—
G-series, nine-day cycle
Active Tzolk'in glyph
—
Original line-art cartouche rendering for the selected day sign.
Active Haab' glyph
—
Original line-art cartouche rendering for the selected Haab' period.
Export & share
Create a portable result link or generate a local PDF report for the selected date. The PDF is created in your browser; no server-side PDF library is required.
Calendar depiction
The outer ring shows the twenty Tzolk'in day signs. The inner ring shows the nineteen Haab' periods. Active positions are highlighted after conversion, while the center gives the combined Calendar Round.
Calendar Round
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—
Active Tzolk'in sign
—
The 260-day cycle combines a number from 1–13 with one of twenty named day signs.
Active Haab' period
—
The 365-day Haab' cycle uses eighteen twenty-day periods followed by five Wayeb' days.
Lord of the Night
—
The Maya G-series is a nine-day count, shown here with epigraphic labels G1-G9 rather than uncertain deity names.
Julian Day Number
—
Long Count total days are calculated as JDN - 584283.
Examples & FAMSI quick-check mode
These examples give students immediate test cases for the converter. The quick-check runner validates the built-in arithmetic against fixed GMT/FAMSI-style anchors using correlation 584283, independent of the currently selected alternative correlation.
Validate against FAMSI-style GMT anchors
This mode is intentionally local. It does not scrape FAMSI; it checks the same GMT 584283 arithmetic against known anchor outputs so a deployed copy can be tested even if external sites are unavailable.
Glyph catalog
The converter embeds original SVG line-art glyphs directly in this page. They are interface reproductions based on standard Maya day-sign and month forms, not scanned or copied manuscript plates. Use them as visual aids alongside Thompson's catalog, Macri and Looper's catalogs, and the Maya Hieroglyphic Database.
Tzolk'in — 20 Day Signs
Haab' — 19 Periods
Sources & computation notes
This v1 is designed for shared hosting: one PHP file, no server calls, no Composer, no API keys, and no database. Computation is deterministic JavaScript running in the user's browser.
Computational basis
- Default GMT correlation constant: 584283.
- Optional alternative constants are available for comparison with warnings.
- Long Count total days: Julian Day Number minus selected correlation.
- Known validation anchor: 2012-12-21 CE -> 13.0.0.0.0, 4 Ajaw, 3 K'ank'in, G9.
FAMSI reference
FAMSI's Date Conversion tool is treated as the comparative reference for GMT-style conversion. The local quick-check mode validates fixed anchors rather than scraping FAMSI at runtime, preserving reliability on shared hosting and during external outages.
Academic caution
Calendar conversion is arithmetic; cultural interpretation of day names, ritual associations, glyph variants, regional usage, and G-series night-lord identifications requires careful source-specific scholarship. This tool should be treated as a converter and visualizer, not as an authority on all Maya calendrical practice.
Suggested bibliography: FAMSI Date Conversion and Calendrics; Smithsonian NMAI Living Maya Time; Thompson 1962; Aveni 2001; Macri & Looper 2003; Macri & Vail 2009; Looper, Macri, Polyukhovych & Vail 2022 Maya Hieroglyphic Database. Glyph renderings are original embedded SVG line art made for this Stella Nova interface.