In John 9, Jesus says, "Are there not twelve hours in the day?" He was implying there were also 12 hours at night. So, what comes between the twelfth hour and the first hour? Nothing, or none, and that is where noon comes from. In the Middle Ages, people disagreed on exactly when "noon" was, and it was often what we would call 3 PM (an hour could be more or less than 60 minutes; it had to be, if there is to be twelve hours of daylight in winter and summer).
From Alfred W. Crosby's The Measure of Reality: Quantification and Western Society, 1250-1600
