Native American symbols are geometric portrayals of celestial bodies, natural phenomena and animal designs. The meaning of the Days and Nights symbol was to signify the passing of time. A clever, simple way to symbolize and record the passing of time. The Native Indians had no clocks but used the environment to measure time. Sunset and sunrise organised the parameters of the day. The cycles of nature, the cold and warm seasons, organised task related work especially agricultural life such as the planting seasons. Rituals and special ceremonies were also scheduled by nature. The summer solstice scheduled the Sun Dance ritual of the Kiowa tribe, the spring equinox scheduled the First Thunder ceremony of the Pawnee tribe and the Zuni tribe celebrated the Great Feast of the Winter Solstice. Most Native American tribes reckoned time by nights, rather than days - distances were calculated by travelling for 'so many nights'.