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 Japan Prime Minister is Shinzō Abe, who re-took office on December 26, 2012. He is the first former Prime Minister to return to office since 1948, and the 5th longest serving Prime Minister to date. The Prime Minister is designated by both houses of the Diet, before the conduct of any other business. For that purpose, each conducts a ballot under the run-off system. If the two houses choose different individuals, then a joint committee of both houses is appointed to agree on a common candidate. Ultimately, however, if the two houses do not agree within ten days, the decision of