In many African societies, I am told, the marketing is done by women. The seventh day was often the day of rest and recuperation, at least in the Western societies from whom we draw our traditions.
In this economy, sellers will adjust their prices over the course of the market day to ensure that they dispose of the entire supply that they have brought to market. This was the world in which the early economists like Adam Smith grew up, and these were the arrangements which they reflected in their models of the economy.