Various formalisms deal with time, and each of them has its own notion of time. When designing a system, it is often desirable to combine several of these formalisms to model different parts. Therefore one has to reconcile execution traces that may use different kinds of time (discrete, continuous, periodic) and different time scales (e.g. minutes, microseconds or even angles in degrees). In this article, we present a deterministic model of time which allows the specification of the coincidence of events that occur on different time scales, as well as instantaneous causality between events. This model supports both event-driven and time-driven specifications.