We consider infrastructure-less highly dynamic networks, where connectivity does not necessarily hold, and the network may actually be disconnected at every time instant. These networks are naturally modeled as time-varying graphs. Clearly the task of designing protocols for these networks is less difficult if the environment allows waiting (i.e., it provides the nodes with store-carry-forward-like mechanisms such as local buffering) than if waiting is not feasible. We provide a quantitative corroboration of this fact in terms of the expressivity of the corresponding time-varying graph; that is in terms of the language generated by the feasible journeys in the graph. We prove that the set of languages L nowait when no waiting is allowed contains all computable languages. On the other end, we prove that L wait is just the family of regular languages. This gap is a measure of the computational power of waiting. We also study bounded waiting; that is when waiting is allowed at a node only for at most d time units. We prove the negative result that L wait[d] = L nowait.