What an awesome question. I know that the mayans used the night sky for watching celestial events from the mountains surrounding their cities. Considering I did a couple of searches I couldn't find much on it though I would hypothesize that the day began more near dawn and would end the next morning. As a possible remedy you might want to reference the i ching's calender considering how similair the 2 systems are...all erronius calender befudlings from outside sources that only seem to convalute the source. ....why couldn't our elders have been more wiser and gotten along?