During the last thirty years, the nature of historical chronology has changed drastically. Fernand Braudel was among the first to show that historical time is neither uniform nor linear, but rather multiple, irregular and socially determined. However, Braudel and his followers have merely carried to an extreme a conceptual revolution already initiated by Marc Bloch in the 1920s. In his studies on the Middle Ages, Bloch identified several time scales: the linear time of Christian history, the circular time of nature and liturgy, the times of the peasant, the townsman and the merchant, and so on. In short, historical time has been transformed in such a way as to prompt a new search for direction and order in historical studies. The new concept of different and irregular time scales forces us to continually redefine the duration of certain phenomena in order to understand them. Chronologies no longer have the same enduring character that provides a definite and reassuring order for the past, as positivism and historicism had claimed to do. In order to be useful at all, chronologies have to be diverse and indicate dates demarcating durations, if only because it is now a generally accepted fact that the time scales of collective mentalities are not the same as those of the economy, politics, or demography.