Simplify the following text for a Grade 13 native English-speaking person.
Original: Joseph Philippe Pierre Yves Elliott Trudeau , ( October 18 , 1919 â `` September 28 , 2000 ) , usually known as Pierre Trudeau or Pierre Elliott Trudeau , was the 15th Prime Minister of Canada from 20 April 1968 to 4 June 1979 , and again from 3 March 1980 to 30 June 1984 .
Simplified: Joseph Philippe Pierre Yves Elliott Trudeau , PC , CC , CH , QC , MSRC , ( born October 18 , 1919 in Montreal , Canada â `` 2000 ) was the 15th Canadian Prime Minister during the 1970s ( 1968 - 1979 ) , and then again from 1980 - 1984 .