Clarence Stanley Day was born in Toronto on 4 March 1908, the second child and first son of Amy Lillian, nee Gilroy, and Walter Arthur Day. He attended Withrow Public School, Humber Collegiate and Riverdale Collegiate. He studied medicine at the University of Toronto and became chief surgical resident at St Michael's Hospital, Toronto. On coming to England he held appointments at the Middlesex Hospital, St Bartholomew's Hospital and St Peter's Hospital for Stone and passed the Fellowship of the College in 1937. During the second world war he served in the 13 RCAMC in England, Belgium and Germany with the rank of Lieutenant-Colonel. He returned to Canada and became Associate Professor at the University of Toronto. In 1942 he married Wilma Emily Nicholson and they had three sons, John, Stephen and Richard, one of whom became a doctor. He contributed several papers on gall bladder surgery to various medical journals. He died on 7 November 1981 aged 73 years.