 Mathematics in indigenous Igbo society is evident in their calendar , banking system and strategic betting game called Okwe . In their indigenous calendar , a week had four days , a month consisted of seven weeks and 13 months made a year . In the last month , an extra day was added . This calendar is still used in indigenous Igbo villages and towns to determine market days . They settled law matters via mediators , and their banking system for loans and savings , called Isusu , is also still used . The Igbo new year , starting with the month Ọ ́ nwạ ́ M ̀ bụ ́ ( Igbo : First Moon ) occurs on the third week of February , although the traditional start of the year for many Igbo communities is around springtime in Ọ ́ nwạ ́ Ágwụ ́ ( June ) . Used as a ceremonial script by secret societies , the Igbo have an indigenous ideographic set of symbols called Nsibidi , originating from the neighboring Ejagham people . Igbo people produced bronzes from as early as the 9th century , some of which have been found at the town of Igbo Ukwu , Anambra state . 
