A great deal has been written about the perception of time before the invention of mechanical timepieces, but the nature of the evidence has led much of this literature to take on an impressionistic, even metaphysical, cast. In the following article, Professor Epstein uses specific data gleaned from the cartularies of thirteenth–century Genoese notaries to investigate more concretely the uses of time and the structure of the business day in Genoa. He concludes that, in this early center of Western commercial activity at least, an impulse toward greater precision in marking the time of day preceded the arrival of the clock.