Chalchiuhtlicue takes the sixth turn among the Yohualteuctin, her governance recurring every ninth date from day six of the tonalpohualli onward, moving independently through the twenty day signs and thirteen trecenas until the full 2340 day period realigns all three counts. A birth falling under her night was read, in the layered method the tonalpouhque practiced, as carrying an association with purification, fluidity and the capacity to be washed clean of a harsher day sign's augury, an interpretation consistent with her governing role over the infant bathing rite even outside the specific night lord reading, since the goddess who cleansed every newborn was naturally read as tempering a difficult birth day with the same cleansing character.
Duran's account of calendar consultation describes parents and priests together weighing a child's day sign, trecena and night lord before settling on the day the naming ceremony itself would be held, sometimes delaying it from the birth date to a more favourable day within the same short span, and a night governed by Chalchiuhtlicue would have been among the readings weighed in that decision. As with the other eight night lords, no fixed pairing existed between Chalchiuhtlicue and any single day sign, since the nine day cycle's independence from the 260 day count means her turn falls across every possible combination in sequence rather than repeating on the same day sign twice within one round.
Sources Cycles of Time and Meaning in the Mexican Books of FateElizabeth Hill Boone with Florentine Codex: General History of the Things of New SpainBernardino de Sahagun; translated by Arthur J. O. Anderson and Charles E. Dibble, Book of the Gods and Rites and The Ancient CalendarDiego Duran; translated by Fernando Horcasitas and Doris Heyden