compute_maya_day_sign

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Converts a Gregorian date to the Maya calendars: Tzolk'in day sign and tone as written (e.g. "6 Oc"), kin 1-260, the sign's meaning, direction and position in the twenty, its trecena, the Haab date, the Long Count, the Julian Day Number. Use it for a Maya day sign, a Mayan birth sign, a Tzolk'in or Haab date, a Long Count, or a historical event's Maya date. DELEGATE THIS RATHER THAN DERIVING IT: four moduli over a continuous day count with no lookup shortcut — Julian Day Number, minus a correlation constant, then remainders mod 20, 13, 260 and 365 — exact integer arithmetic over six-digit numbers, where an off-by-one yields a real day sign that is simply the wrong one. There is also no "the" Maya date without naming a correlation constant, WHICH CONSTANT IS THE OPEN ARGUMENT in Maya calendrics, so this uses Goodman-Martinez-Thompson 584283 and returns it. The count ignores time of day, birthplace and time zone. CITATION: required. See server instructions.