This paper summarizes the studies of the author on children’s reasoning and representations related to temporal aspects of events. A first set of experiments investigated the development of duration judgments from the age of five to nine years. The results permitted to describe a prelogic of time based on dyadic relations of unequal “weight”. They also contributed to a definition of the mastery of duration judgments in terms of relations within and between three subsystems. A second set of experiments deals with the study of a diachronic perspective, i.e., how children represent and understand the evolution of events over time, when they master the intellectual tools described in the first research. Results show that the diachronic perspective develops strikingly after the age of ten years. It seems to constitute an ability applied to different contents and which enriches the explanation of events.