The Lakota (Sioux) Oyate observed the changes occurring with each new moon. Each moon was identified in descriptive terms by the occurrences of that month.
The Lakota (Sioux) also observed the changes in the stars in the night sky. Certain star constellations appeared during each season. From these observations, they determined the equinox and the changes in the seasons.
The Lakota (Sioux) identified 13 months in a year because of the 13 new moons; each moon has 28 days from one new moon to the next.
The Lakota (Sioux) Oyate also observed some creatures that reflected natural phenomena. For instance, the keya — turtle has 13 large scales on its back, and 28 small scales around the shell. Because of these and other natural occurrences the keya became an important symbol in Lakota (Sioux) society.
The spirit of the keya represents the guardian of life, longevity and fortitude. An amulet in the shape of a keya is made for every newborn baby in many families. A part of the umbilical cord from the child is placed inside the keya, and the amulet was tied to the cradleboard.
Keya protects the newborn from mni watu — bacteria or germs that can cause illness for the baby. The keya was also used as a learning tool. Later, it was put away until the child could take care of it and treat it respectfully. Then, it was given back to the child to be worn on a costume or ceremonial dress.
The Lakota (Sioux) Oyate observed and studied many beautiful natural phenomena on Unci Maka — Grandmother Earth. They recorded many of these lessons on winter counts and taught younger generations to be observant and respectful to all of creation.
The Lakota (Sioux) year began in March with the first day of spring. The “Calling Back of Thunder Ceremony” — held on He Wakinyan Hohpi — Harney Peak – began the New Year.