This article describes how this special issue was conceived, the rationale behind it and the principal lessons to be drawn on the subject of working time in industrialized countries. It shows that we may be at a turning point in history; a process of fundamental transition is occurring between one epoch-the industrial era during which linear, uniform working time, based on a specific mode of production and set of professional relationships, was imposed as the central pivot around which the whole of society was organized-and another, characterized by a noticeable reduction in, but above all a significant diversification of the nature of working time, ie rapid change in its content and form. We are witnessing the shift from a single temporality-time imposed synchronistically-to a plural temporality-individually chosen working time and variable hours.