That fifty two year return was the calendar's most consequential moment, because the xiuhpohualli's year count and the two hundred sixty day tonalpohualli it ran alongside both reached their starting point together only once every fifty two years, a combined cycle the Aztecs called the xiuhmolpilli, the "binding of the years." Its close was marked by the Toxiuhmolpilia, the New Fire Ceremony, most famously performed atop the Hill of the Star near Tenochtitlan: household fires across the empire were extinguished in advance, and a new flame kindled on the chest of a sacrificial victim at the ceremony's climax was carried out to relight them, an act understood to guarantee the sun and the world would continue rather than end. The original state cult version of the xiuhpohualli did not survive the Spanish conquest as a functioning civil calendar; the veintena festivals it structured were suppressed along with the priesthood that ran them. It has not vanished from practice, though.
Contemporary Mexica and Danza Azteca revivalist communities, both in Mexico and among Chicano and Indigenous groups in the United States, have reconstructed elements of the xiuhpohualli for ceremonial use today, work that draws on colonial era sources like the Florentine Codex but necessarily differs from the pre-conquest state cult it descends from.