Flag of Zanzibar yellow cloves was added to the flag. On 12 January 1964, John Okello overthrew the Sultan of Zanzibar and adopted a black-yellow-blue tricolour as the flag of the People's Republic of Zanzibar and Pemba. On 29 January, the country's flag was changed to a blue-black-green tricolour with a thin white stripe at the hoist. This design, which was based on the flag of the Afro-Shirazi Party, was the longest-lived of the post-independence flags and eventually formed the basis for the current flag. On 26 April 1964, Zanzibar united with Tanganyika to form the new country of Tanzania and Zanzibar's old
Zanzibar century. Persian, Indian, and Arab traders used Zanzibar as a base for voyages between the Middle East, India, and Africa. Unguja, the larger island, offered a protected and defensible harbor, so although the archipelago offered few products of value, traders settled at Zanzibar City ("Stone Town") a convenient point from which to trade with the other Swahili coast towns. The impact of these traders and immigrants on the Swahili culture is uncertain. During the Middle Ages, Zanzibar and other settlements on the Swahili Coast were advanced. The littoral contained a number of autonomous trade cities. These towns grew in wealth