This paper describes a Time Warp mechanism designed to exploit temporal uncertainty (TU) in distributed simulation. Novel in the proposed approach are: (a) a formal event model where events are assigned time intervals instead of usual punctual timestamps; (b) an aggressive cancellation technique, which shifts overheads from communications to computation; (c) an implementation in Java, which deploys a framework for distributed simulations over Internet. The paper introduces the Time Warp mechanism and reports some experimental results using a large PCS model. The experiments confirm that TU is able to speedup simulation without compromising the accuracy of the results.