Concept
Tzolk’in
The 260-day sacred Maya calendar: 13 numbers cycling with 20 day names. Still kept, as Chol Q’ij, by daykeepers in highland Guatemala.
Unknown Maya scribe; photograph of a public-domain manuscript, “Dresden Codex, page 49”, Public domain, via Wikimedia Commons
Why 260 is unresolved: it is near a human gestation, near some maize cycles, and near the Sun’s zenith passages at certain tropical latitudes, and it is 13 × 20. The explanations are not mutually exclusive. Each day carried a character used in divination. It is not a solar year.