Yucatan Before and After the Conquest, by Diego de Landa, tr. William Gates, , at sacred-texts.com
This page having already been published in Morley's Inscriptions at Copan (Carnegie Inst., 1921), as traced in facsimile, transcribed and translated with full notes, by the present writer, needs little more description here than as given above on page 121. It gives a series of events from 1533 to 1545, in Maya, with the dates given both in full Maya and European terms. We learn that there was a maya-cimlal or general mortality in 1533 (the very year that the elder Montejo retired beaten on his first attempt at conquest), the killing of the "rain-bringer" Napot Xiu at Otzmal in 1536, a hurricane in
[paragraph continues] 1538, the founding of Mérida by the Spaniards in 1542, "and the beginning of the tributes, by the aid of those of Maní, on the day 5 Ahau, the 17th of the month Tzec," the battle at Tzitzomtun in 1543, and the coming of Christianity in 1545, with the arrival of the six Franciscan friars. "Copied on May 29th, 1685, from an ancient book, namely in characters as they are called, anares. I, don Juan Xiu."
Accurate as the dual dating in this paper is, it was rejected as a basis for correlation by Morley and myself, after long arguments, as being contrary to what we then believed were settled facts as to the periods of occupation and non-occupation at Chichén Itzá, and similar points. Finally we agreed on the correlation given by him in Appendix II to his Copan book, based on a time-reckoning in vogue among the eastern Yucatecans or Itzás; owing to the elaborate system of triple checks in the Maya calendar, the variation between the Itzá and Xiu counts involved a difference of 260 years in the actually elapsed time from the zero-date of the Maya time reckoning, now finally fixed at August 13, 3113 B.C., or Julian Day 584, 259. Since then, later discoveries have corrected the errors above, and shown conclusively the complete accordance of Juan Xiu's page with the entire series of monumental and other dates, and giving us a definite check date of Nov. 13, 1539, as expressible in Maya terms by 11.16.0-0-0, 13 Ahau, the 8th of the month Xul, that is, 4720 'mathematical' 360-day years from the above zero-date of the Mayas.
So much we owe to Juan Xiu, Xiu XI, the last of the recognized Xiu local governors under the Spanish régime, at almost the end of his three score and ten years.