section_path: Calendar/Correlation of the Long Count calendar
section_name: Correlation of the Long Count calendar
paragraph_text: Correlation of the Long Count calendar
  
  Although the Calendar Round is still in use today, the Maya started using an abbreviated Short Count during the Late Classic period. The Short Count is a count of 13 kʼatuns. The Book of Chilam Balam of Chumayel contains the only colonial reference to classic long-count dates. The most generally accepted correlation is the Goodman-Martínez-Thompson, or GMT, correlation. This equates the Long Count date 11.16.0.0.0 13 Ajaw 8 Xul with the Gregorian date of 12 November 1539. Epigraphers Simon Martin and Nikolai Grube argue for a two-day shift from the standard GMT correlation. The Spinden Correlation would shift the Long Count dates back by 260 years; it also accords with the documentary evidence, and is better suited to the archaeology of the Yucatán Peninsula, but presents problems with the rest of the Maya region. The George Vaillant Correlation would shift all Maya dates 260 years later, and would greatly shorten the Postclassic period. Radiocarbon dating of dated wooden lintels at Tikal supports the GMT correlation.