Accession to the London Act (1934) by the Federation of Rhodesia and Nyasaland: September 25, 1957; Entry into force: April 1, 1958. Signature of the Lisbon Act (1958): October 31, 1958; Accession by Southern Rhodesia: September 2, 1964; Entry into force: April 6, 1965. Declaration of succession to the Lisbon Act (1958) by the Republic of Zimbabwe: September 29, 1981. Entry into force date given as date of independence.