Clive Hart Day (February 11, 1871 – July 27, 1951) was an American college professor and writer on economics history, born at Hartford, Conn. He was chief of the Balkan Division of the American Commission to Negotiate Peace (Paris, 1918-19).
After graduating from Yale University in 1892, where he was a member of Skull and Bones,[1]:10-11 and won the John Addison Porter Prize, he took postgraduate studies there and at the universities of Berlin and Paris, taught history and economics at the University of California for three years and economics at Sheffield Scientific School (Yale) for two years, and in 1907 was appointed professor of economic history in Yale University.