United Republic of Tanzania
Who & why: Tanganyika and Zanzibar formally unite on 26 April 1964, three months after the Zanzibar Revolution, forming the United Republic of Tanganyika and Zanzibar under President Julius Nyerere; the country is renamed the United Republic of Tanzania later that year, combining the two territories' names. Zanzibar keeps its own president, legislature, and constitution as a semi-autonomous part of the union to this day — a genuinely distinctive federal-style arrangement within a single sovereign state.
What it represents: a black diagonal band with thin gold fimbriation splits the flag into a green triangle (the mainland's agriculture and land) and a blue triangle (Zanzibar and the Indian Ocean); the design deliberately merges Tanganyika's green-gold-black-gold-green flag with Zanzibar's own blue-black-green tricolor into one union banner.
Wikipedia's infobox gives the adoption as 30 June 1964. FOTW: Tanganyika and Zanzibar merged on 26 April 1964 and the union flag recombined the two predecessors, the lower green stripe of Tanganyika's flag taking Zanzibar's blue and the stripes rearranged diagonally; the name Tanzania was adopted 29 October 1964; the 1971 Flag Act gives the flag legal validity from 26 April 1964.
- Flag of Tanzania — Wikipedia compiled
- Tanzania (Flags of the World) — Flags of the World (CRW Flags) compiled
- Tanganyika (1961-1964) — Flags of the World (CRW Flags) compiled
Not established: The sources differ on the day (Wikipedia 30 June 1964, FOTW 26 April 1964 for the union and flag), but agree on 1964; the colour meanings and swatch values were not compared.