The Long Count uses a mythic-era anchor date written as 13.0.0.0.0 (4 Ajaw 8 Kumk’u). Under the widely used GMT correlation, this corresponds to 3114 BCE-08-11 (proleptic Gregorian), providing a fixed point for converting Long Count counts to absolute dates.
Large-scale surveys of architectural orientations in southern Mesoamerica indicate systematic tracking of solar and other celestial cycles consistent with use of calendrical intervals (including those linked to the 260-day system), pushing indirect evidence for organized calendrical astronomy back to roughly 1100–750 BCE.
Painted mural fragments from San Bartolo, Guatemala, in sealed Late Preclassic contexts (radiocarbon-anchored to 300–200 BCE) include the day record “7 Deer”, widely cited as the earliest secure calendar notation from the Maya region for the 260-day divinatory cycle (Tzolk’in).
An inscribed wall panel known as Stela 2 from Chiapa de Corzo (Chiapas, Mexico) preserves an early Long Count reading (7.16.3.2.13), commonly correlated to 36 BCE, and often cited as the oldest discovered Long Count date.
Stela C at Tres Zapotes (Veracruz, Mexico) bears the Long Count 7.16.6.16.18, commonly correlated to 32 BCE, among the earliest firm Long Count monuments and associated with Isthmian/Epi-Olmec scribal traditions.
At El Baúl (Pacific coastal Guatemala), Stela 1 carries an early Long Count date (7.19.15.7.12), often correlated to 37 CE, illustrating that Long Count usage spread beyond a single region in the Late/Terminal Preclassic–Early Classic transition.
Takalik Abaj monuments include very early Long Count dates; Stela 5 is often reported with dates including 8.4.5.17.11 (126 CE) (and another early date on the same monument in some readings), reflecting early calendar writing at the Maya–Isthmian interface.
La Mojarra Stela 1 (Veracruz, Mexico) contains multiple Long Count notations (including 8.5.3.3.5 and 8.5.16.9.7 in common presentations), linked to the Isthmian/Epi-Olmec script tradition and demonstrating mature integration of Long Count with Calendar Round components.
The Tuxtla Statuette (Veracruz region) includes an early Long Count date (commonly given as 162 CE), another key artifact tying early Long Count practice to the Isthmian Gulf Coast cultural sphere.
Stela 29 from Tikal records the Long Count 8.12.14.8.15, widely treated as Tikal’s earliest securely dated monument (Early Classic), marking the prominent adoption of Long Count monument-dating in the central Maya lowlands.
The Dresden Codex preserves a detailed Venus synodic table built around the 584-day cycle between heliacal risings, illustrating advanced computational astronomy integrated with ritual calendar practice (and larger commensurations such as 5 Venus cycles = 8 Haab’ years).
The Madrid Codex (Codex Tro-Cortesianus)—generally dated to the late Maya period (~1400 CE)—contains extensive material on divination/astrology and ritual year practices, showing the persistence of calendrical-astronomical knowledge into the Postclassic.
The Codex Borgia (Central Mexico) is largely devoted to the tonalpohualli, the 260-day divinatory calendar, illustrating the broad Postclassic development of calendrical divination traditions beyond the Maya area.
Mesoamerican calendrical systems and astronomical observation (Preclassic–Postclassic)
