The tonal day
The book of days, and why there is no single count today
What it covers
What a tonalámatl was and how it was consulted, and why five different correlations are in circulation today.
The full entry is in Spanish, and here is why
What you have read above is this project's own summary of the tonal day. The full entry — the part that rests on the sixteenth-century sources — has not been translated, and that is a decision rather than an omission.
We chose not to touch the primary text. Those sections quote Sahagún, Durán and the codices in their own words, often in sixteenth-century Castilian. A quotation carried across stops being a quotation: it loses the register, the ambiguity and the exact wording someone might want to check against a facsimile.
In Spanish the entry carries:
- El libro de los días
- Quien lo leía
- Lo que se rompió
- Cómo se vuelve a amarrar
- Por qué no coinciden
- Las que trae esta app
- Cuál elegir
Read the full entry in the original Spanish → Nahuatl names and terms are identical in both versions.
The book of days
Tonalamatl joins two words: tonalli, the day and its charge, and amatl, the paper. It was a strip of bark paper folded like an accordion holding the 260 combinations, each with its marks.
It was not an almanac for looking up the date. It was for reading what a day brought: whom it suited to name how, when to set out, when to wait.
It was not the business of one city or one people. Every people of Mesoamerica knew and used this count, and the day that bore a name in Mexico bore the same or the corresponding one from the Pánuco to Nicaragua, and from Sinaloa to Yucatán.
Nor was it new. It is found already at Monte Albán I, in Oaxaca, centuries before the Christian era, and from it come the reckonings of Maya, Zapotec, Mixtec, Totonac, Huastec, Teotihuacan, Toltec and Mexica. Where it came from is not known.
Who read it
The tonalpouhqui was the counter of days. He did not divine: he read. He looked up the day's position in the book and interpreted it together with what he was asked.
When someone was born he was consulted, and if the day came charged the naming could be moved to a neighbouring, more favourable day. The count was not a sentence: it was material to work with.
In the plural they were called tonalpouhque, and their office was to read the signs of lucky and unlucky days in the books that were called, for that reason, tonalamatl: «paper or book of the days».
What was broken
The books were burned almost entirely, and those that remain can be counted on one hand. The running count — sustained day by day, skipping none — stopped being kept in public.
That is the fracture. A continuous count survives only if someone keeps counting it; when it is interrupted, recovering it means tying it again to a known date.
How it is tied back
You look in the sources for a day where both things are known: its date in the European calendar and its name in the count. With a single such pair the whole count is fixed, backwards and forwards.
That is why the correlations are named after whoever proposed them. They are not opinions: they are anchors, and each one chose its own from what the sources left.
Why they do not agree
The sources do not all say the same thing, and some contradict each other. Changing the anchor shifts the whole count by a few days, and then the same birth falls on a different sign.
There is a second, deeper difference: not all of them start the day at the same hour. And if the day begins at another moment, the sign changes for whoever was born before dawn.
Which to choose
This app does not arbitrate. It carries several, says where each comes from and what it was tied to, and leaves the choice in Settings. Whichever is set is named on every screen that computes.
That they do not agree is not a defect of the counts but the mark of what was lost. Presenting one as the true one would cover that mark.
How to cite this page
Alma Mexica, «The tonal day», The documents. Revised 2026-09-17. https://almamexica.org/en/document/dia-tonal/