Xiuhpowalli · Tonalpowalli
Understanding the Mexican Count of Days
A free, self-paced course in six modules. You will learn how the 260-day count of days and the 365-day solar year work together, how the sky and the architecture of Tenochtitlan keep the calendar honest, and how to place any modern date inside the count using Rubén Ochoa's correlation.
How it works
Watch the lecture, do the readings, then answer the checkpoint questions before moving on.
What you need
No prior study is assumed. A notebook helps — much of this is learned by counting days by hand.
Time to finish
Roughly six sessions. Each module is one video lecture plus supporting material.
The curriculum
Six modules
- Module 1Sky, Sun and the Origins of the CountWhere the count comes from: the movement of the sun and sky as observed from Mesoamerica, the cosmology of the Suns, and why a calendar was inseparable from astronomy and ceremony.1 lecture · 1 supplemental video · 1 reading
- Module 2Reading the Horizon: Alignments and the Templo MayorHow architecture keeps time. Buildings at Tenochtitlan, Teotihuakan and across Mesoamerica were oriented to sunrise events on the horizon, turning cities into instruments for anchoring the year.1 lecture · 3 supplemental videos · 2 readings
- Module 3The Count of Days: Twenty Signs, Thirteen NumbersThe engine of the system. Twenty day signs turn against the numbers 1 through 13, producing 260 unique days, thirteen-day trecenas, and the sequence recorded in the codices.1 lecture · 1 supplemental video · 2 readings
- Module 4The Solar Year: Veintenas, Nemontemi and Year BearersThe 365-day side of the system: eighteen veintenas of twenty days, the five nemontemi that close the year, the ceremonies attached to each period, and the four signs that can bear a year.1 lecture · 1 reading
- Module 5Correlation: Fixing the Count to a Modern DateThe problem every student hits — which Mexika day is today? This module works through correlation, the reasoning behind Rubén Ochoa's alignment to the observed equinox sunrise at the Templo Mayor, and why competing correlations disagree.1 lecture
- Module 6Working the Calendar: Practice and Ceremony TodayPutting the system to use — reading a date in full, tracking the year through its veintenas, keeping the new year, and treating the auguries as historical testimony rather than prescription.1 lecture · 1 reading
A note on sources
The lectures and readings collected here are the Mexika Calendar System class produced by Chimalli Media. The correlation used throughout — anchoring the turn of the solar year to the equinox sunrise observed at the Templo Mayor — follows the work of Rubén Ochoa. Day auguries quoted in the course come from Book 4 of the Florentine Codex and are given as historical testimony of how the day keepers read the count, not as prescription.