I have elsewhere argued that farmers do not need celestial calendars to tell them when to plant. They go by biological clues in their environment. A quote I once read, the source of which is long lost in time, stated "it is time to plant corn when the leaves on the trees are the size of squirrel's ears." Now it may be that they do follow such calendars, but that is because of religious dogma, not out of physical necessity or their own lack of skill. Such beliefs are imposed upon them by leaders. In any case, and for whatever purpose it was intended, this is another fascinating, and important discovery about the knowledge of the ancient people of that area.
(All photos: David Purcell/NPS, used with permission.)