This article records tradition as it has been passed down and reported. Its sources are not yet part of the atlas's verified catalogue.
Count gathers five reckonings that measure time by running a fixed count forward rather than by tracking the sun or moon through a repeating cycle, and the group divides between two unrelated Mesoamerican traditions and one modern convention.
The Tzolkin is the Maya sacred count of 260 days, made by running twenty named day signs against the numbers one to thirteen so a pairing returns only after 260 days; it carries no year of its own and is used to time ritual, to divine and to name a person for the day they were born on, and day keepers in the Guatemalan highlands still run it today. The Aztec Tonalpohualli is the same 260 day structure under a different tradition, pairing twenty day signs with the numbers one to thirteen so no combination repeats, ordering divination and naming with each thirteen day trecena under its own patron deity. Meshed with a 365 day year, either count produces a calendar round that repeats every fifty two years, which the Maya Calendar Round names directly.
The Maya Long Count departs from both by counting continuously from a mythic creation date, dividing time into progressively larger units running from the single day to the baktun of a hundred and forty four thousand days. Common Era is the odd member out, not a calendar at all but a reckoning of where a year count begins, devised by Dionysius Exiguus in 525 to calculate Easter and now used as a religiously neutral label over a Christian calculation.