Principal English Translation:
the count of the months or the phases of the moon
Fr. Bernardino de Sahagún, Florentine Codex: General History of the Things of New Spain; Book 10 -- The People, No. 14, Part 11, eds. and transl. Arthur J. O. Anderson and Charles E. Dibble (Santa Fe and Salt Lake City: School of American Research and the University of Utah, 1961), 88.
Attestations from sources in English:
Chapopotli (bitumen) is said to come onto the shore of the sea from the ocean in accordance with the time count and the phases of the moon (metztlapoalpan) in the Florentine Codex.
Fr. Bernardino de Sahagún, Florentine Codex: General History of the Things of New Spain; Book 10 -- The People, No. 14, Part 11, eds. and transl. Arthur J. O. Anderson and Charles E. Dibble (Santa Fe and Salt Lake City: School of American Research and the University of Utah, 1961), 88–89.