September 12, 2026 Dr. Geraldine Patrick Encina: “A Reinterpretation of Eclipse Dates at Xochicalco.”
Dr. Patrick Encina has recently found that Xochicalco has one of the few standing-on-site stelae (the Two Glyph Stela) whose date is that of its zenith passage, May 14, 747. Equally relevant is the fact that the year recorded on it (10 Reed, Otomian version) positions May 14 two days before a solar eclipse on May 16, 747 CE, which is the first of a sequence of three eclipse dates recorded on the site. The second and third dates are carved on the southwest talud of the Pyramid of the Feathered Serpents. The northeast talud of this pyramid shows the first two of another sequence of three dates, the wrongly interpreted 5 Casa and 11 Mono, which mark two eclipses in 743 CE separated by half a moon-year through an iconographic resource presented in the Fejérvary-Mayer codex. Importantly, that 11 Mono is at the start of a five-day lapse of astronomical observations that must have occurred inside the zenith chamber “Cueva del Amate” until the total eclipse that turned Xochicalco dark at noon on July 28, 743 CE. These readings can only be made when using the correlation proposed by Dr. Patrick Encina for the Olmec and Maya calendrical system (since 2013), and the Otomian calendrical system (since 2015). The former system keeps 0 Pop on August 13 and marks the start of 13 Bak’tun (4 Ajaw 8 Cumk’u) on July 27, 3117 BCE, while its completion (4 Ajaw 3 Kank’in) is on May 3, 2013 rather than December 2012. The astronomical precision of this correlation acquires archaeological relevance because both calendrical systems use synchronic 260-k’in cycles, permitting correct readings when glyphs for this component of the Calendar Round are used interchangeably, as is the case on the Xochicalco Two Glyph Stela whose inscription has the Maya day glyph 9 Ajaw” and the Otomian year glyph “10 Anxithi” or 10 Reed.
Dr. Geraldine Patrick Encina lives with her family in the Highlands of Mexico, in the original Zanbatha “Valley of the Moon”, now Valle de Toluca. She holds a PhD with a specialty in Ethnoecology from El Colegio Mexiquense (2007) and did a Post Doc on Mesoamerican Conceptions of Time-Space in UNAM-Morelos (2012). As an Ethnoecologist, Cultural Astronomer and member of the Sociedad Interamericana de Astronomía en la Cultura, Geraldine has generated extensive knowledge about the astronomical, ecological, agricultural and philosophical underpinnings of ancient Mesoamerican timekeeping systems. This theory and practice is helping study groups of Yucatec and Otomi bioregions recover long lost calendars and astronomical tables.
This lecture is now available for members only in Meeting Archives.