Mesoamerican calendars prognostic power for the coming year. Therefore, People tried to do as little as possible on these days, and a person who was born during the nemontemi was considered unlucky. Since both the 260-day and the 365-day calendar repeat, approximately every 52 years they reach a common end, and a new Calendar Round begins. This 52-year cycle was the most important for most Mesoamericans, with the apparent exception of the Maya elite until the end of the Classic Era, who gave equal importance to the Mesoamerican Long Count calendar. According to their mythology, at the end of one of these
Mesoamerican Long Count calendar The number of leap days, keeping in mind that the year 600 is not a leap year, is 10. Subtracting that from 317 remainder days is 307; in other words, the 307th day of the year 644 AD, which is November 3. To summarize: the Long Count date 9.10.11.17.0 corresponds to November 3, 644 AD, in the "Proleptic Gregorian calendar". To convert a Julian day to a Julian/Gregorian astronomical date (Proleptic Julian calendar before 46 BC): Use an astronomical algorithm such as the "Method of Meeus" to convert the Julian day to a Julian/Gregorian date with astronomical dating of negative