An Ah K'in, literally something close to "he of the days" or "he of the sun," held responsibility for the two interlocking calendars that structured Yucatec Maya religious life, the 260-day sacred count and the 365-day Haab civil year, and for the divinatory almanacs, such as those preserved in the Dresden and Madrid Codices, that paired specific days and periods with particular gods, omens and appropriate or forbidden activities. Nothing of consequence in community life, planting, marriage, warfare, the timing of a festival, was properly begun without consulting an Ah K'in's reading of whether the day was auspicious.
Diego de Landa, whose Relacion de las cosas de Yucatan is a primary colonial source on pre-conquest Yucatec religion despite his own role in burning Maya bark-paper books, describes a priestly hierarchy topped by a high priest with Ah K'in serving under him, trained from childhood in the sons of priests and nobles, instructed in the sciences the Maya recognized: the count of the years, the calendar of festivals, the ceremonies proper to each, and forms of divination. The office combined what a modern reader might separate into astronomy, religious administration and ritual timing into a single, socially essential priestly specialization.