Researchers used LiDAR to look at the astronomical orientations of 415 Olmec and Maya ceremonial structures in Mesoamerica from between 1100 BCE and 250 CE. They found that many of the structures were oriented with the solstices, quarter days, or lunar cycles of a 260-day calendar. In short, they are positioned in a way that corresponds with the sunrises on February 11 and October 29, which are 260 days apart. It was previously thought that this type of calendar went back only as far as 300 BCE, so this study suggests that the Maya understood the stars much earlier than previously thought. No one is quite sure why they used 260 days, but the researchers favor theories involving some kind of numerological significance, or the scheduling of rituals.