code: def to_tzolkin(jd):
      '''Determine Mayan Tzolkin "month" and day from Julian day'''
      lcount = trunc(jd) + 0.5 - EPOCH
      day = amod(lcount + 4, 13)
      name = amod(lcount + 20, 20)
      return int(day), TZOLKIN_NAMES[int(name) - 1f to_tzolkin(jd):
      '''Determine Mayan Tzolkin "month" and day from Julian day'''
      lcount = trunc(jd) + 0.5 - EPOCH
      day = amod(lcount + 4, 13)
      name = amod(lcount + 20, 20)
      return int(day), TZOLKIN_NAMES[int(name) - 1]
docs: Determine Mayan Tzolkin "month" and day from Julian day