Abstract : Today's consumer electronics industry uses modeling and simulation to cope with the complexity and time-to-market challenges of designing high-tech devices. In such context, Transaction-Level Modeling (TLM) is a widely spread modeling approach often used in conjunction with the IEEE standard SystemC discrete-event simulator. In this paper, we present a novel approach to modeling time that distinguishes between instantaneous actions and tasks with a duration. We argue that this distinction should be natural to the user. In addition, we show that it gives us important insight and better comprehension of what actions can overlap in time. We are able to exploit this distinction to parallelize the simulation, achieving an important speedup and exposing subtle software bugs related to parallelism. We propose a set of primitives and discuss the design decisions, expressiveness and semantics in depth. We present a research simulator called jTLM that implements all these ideas.