The Igbo calendar (Ògụ́àfọ̀ Ị̀gbò) is the traditional calendar system of the Igbo people of Nigeria which has 13 months in a year, 7 weeks in a month, and 4 days in a week plus an extra day at the end of the year. The calendar has its roots steeped in ritualism and symbolism; many parts of the Igbo calendar are named or dedicated to certain spirits (|Mmuo) and deities (Alusi) in the Igbo mythology. Some of the spirits and deities were believed to have given the Igbo people knowledge of time. The days, also known as market day, also correspond to the four cardinal points, north, south, east, west.