The measurement of all times that these Indians [the Mexicans] carried out was as follows: the largest measurement of time was of 104 years and they called it a century; half of this period, which is 52 years, they called a sheaf of years. This number of years they have counted since ancient times; it is not known when it began, but they quite faithfully believed that the world would come to an end at the termination of one of these sheafs, and they had prophecies and oracles that the movements of heaven would cease then, and they took for a signal the movement of the Cabrillas (Pleiades) in relation to the night of the feast, which they called Toxiuh molpilli, for on that night the Cabrillas were in the middle of the sky at midnight, corresponding to this Mexican latitude. {See also Aldebaran}

On this night they lit the new fire, and before they lit it they put out the fires of all the provinces, towns and houses of all this New Spain, and all the satraps and ministers of the temples went in great procession and solemnity. They went from here, from the Temple of Mexico [Templo Mayor] early at night; they went to the summit of that hill near Ixtapalapa and which they call Uixachtecatl; and they climbed to the top at nearly midnight, to where there was a solemn cu [Mayan name meaning 'god and temple', a term that the conquistadores learnt when they landed in Yuctan] made for that ceremony; and if they were too early, they waited until they arrived; and when they saw that they [the Cabrillas or Pleiades] passed the zenith, they understood that the movement of the heavens was not to cease, and that it was not the end of the world, but that it would last another 52 years, and that the world surely would not come to an end. At this hour great multitudes were in the hils surrounding this province of Texcoco, Xochimilco and Quahtitlan, waiting to see the new fire, that was the signal that the world would continue on; and as the satraps brought out the fire with great ceremony in that hill's cu it then appeared all around the hills, and when those who were there saw it, they were so happy that they yelled and their yells reached up to heaven, for the world was not coming to an end and the undoubtedly had 52 more years.

Gilbert and Cotterell:1995 129-130. {Quoting Sahagun}

Now when, using the computer, I checked on what day in 1507 the Pleiades crossed the meridian at midnight, I was very surprised to find that it was 11 November This lies right in between 16 Xul (8 November) and the start of Yaxkin (13 November). We know that the festival, with its fast lasted for five days, so this must have been during the period when the Pleiades were crossing the meridian at midnight each day, the central day of this period having the closest timing. So it seems that for the Maya the New Fire ceremony was an annual event, though for the Aztecs it was only celebrated once every 52 years.

Gilbert and Cotterell:1995 133-134 . In his book Aztec and Maya Myths, Professor Karl Taube of the University of California writes that the New Fire festivals were closely connected with the idea of world renewal after the Flood. In effet they were annual celebrations of an event believed to have taken place when the world was recreated by the gods at the beginning of our own age. . .

Gilbert and Cotterell:1995 135 .