Aztec (Mexica)

Xiuhpōhualli & Tōnalpōhualli · the Caso correlation

The Mexica kept two interlocking counts, as the Maya did: the 365-day Xiuhpōhualli of eighteen twenty-day veintenas plus five unlucky nemontemi, and the 260-day Tōnalpōhualli of twenty day-signs against thirteen numbers. Dates follow the Caso correlation, anchored to the fall of Tenochtitlan on 23 August 1521 — recorded as 1-Cōātl. The two counts ran in step with the Maya, so the day-sign here matches the Tzolkʼin’s.

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