Mesoamerican architecture there is no evidence that this phenomenon was the result of a purposeful design intended to commemorate the equinoxes. Much Mesoamerican architecture is also aligned to roughly 15° east of north. Vincent H Malmstrom has argued that this is because of a general wish to align the pyramids to face the sunset on August 13, which was the beginning date of the Maya Long Count calendar. However, recent research has shown that the earliest orientations marking sunsets on August 13 (and April 30) occur outside of the Maya area. Their purpose must have been to record the dates separated by
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