 Day was born on 24 December 1955 in Middle Swan, Western Australia to John and Myfanwy Day.His father, who survived the Second Battle of El Alamein, died when Day was 17 years old.Attending Guildford Grammar School, Day later completed a Bachelor of Science, and a Bachelor of Dental Science at the University of Western Australia going on to work at the Perth Dental Hospital as well as other clinical situations including Canning Vale Prison.