TURTLE SHELLS WERE USED AS CALENDARS BY THE INDIANS

All turtle shells have 13 moons and 28 days. This is equivalent to 364 days plus one day of rest. The ancient Scots, Norse, Polynesians, and Native Americans all recognized the wisdom of the turtle and adhered to a 13-month calendar; after all, there are 13 moon cycles in a year and 27-29 days each cycle.

It's almist as if the system erased one month to break the link between humans and the sun. moon, and stars, which serve as a gigantic clock.