Timing is a central concern in critical embedded systems. Such systems must interact with a physical environment in a timely fashion. The critical point here is not average performance but guaranteed performance which must be good enough for the given environment. In this introduction to the Festschrift dedicated to Wang Yi on the occasion of his 60th birthday, we give an overview on the contributions of Wang Yi to the analysis and the construction of real-time systems and to the related contributions to this volume.