Prime Minister of Australia prime minister, otherwise William McMahon63. Robert Menzies was the oldest person to ever be prime minister, leaving office at 71 years old. The longest-serving Prime Minister was Sir Robert Menzies, who served in office twice: from 26 April 1939 to 28 August 1941, and again from 19 December 1949 to 26 January 1966. In total Robert Menzies spent 18 years, 5 months and 12 days in office. He served under the United Australia Party and the Liberal Party respectively. The shortest-serving Prime Minister was Frank Forde, who was appointed to the position on 6 July 1945 after the death of
Prime Minister of Denmark Since King Christian X never accepted the resignation of the government, it existed de jure until a new cabinet was formed on 5 May 1945. The twentieth century was dominated by Social Democratic Prime Ministers leading left-wing coalitions; Social Democratic Prime Ministers were in power nearly continuously from 1924 until 1982. The first Prime Minister from the Conservative People's Party, Poul Schlüter, came to power as the head of a broad centre-right coalition in 1982. The centre-right coalition ruled in 1993, last for eleven years, made it became the longest centre-right government in Denmark history since 1920s. In November 2001