the Dakota lunar calendar

One of my favorite parts of the Gibbs farm experience is the Dakota lunar calendar and learning they ate muskrat during the spring of the year and not during any other time. They muskrat left sores in their mouths at other times or the year because of a chemical they emit. 

Also learned turtle shells were used as a calendar. 13 big plates for the 13 moons and 28 small fringe plates for the days between moons.