Representing temporal information is a recurrent problem for biomedical ontologies. We propose a foundational ontology that combines the so-called threedimensional and four-dimensional approaches in order to be able to track changes in an individual and to trace his or her medical history. This requires, on the one hand, associating with any representation of an individual the representation of his or her life course and, on the other hand, distinguishing the properties that characterize this individual from those that characterize his or her life course.