A critical issue in the field of time perception is whether or not explicit judgments about time are processed by some internal clock mechanism. A subsequent issue is whether or not this clock, if any, is central (i.e., is the same for a large range of durations, for whatever way of marking the intervals to be processed). There are several ways of marking time, including the use of signals delivered from different sensory modalities. In other words, do we have sensory specific representations of time, or is there an amodal—central—mechanism (Bueti, 2011)? This fundamental question is addressed here with an emphasis on the discrimination of brief empty time intervals. More specifically, intermodal intervals are of interest, an intermodal interval being marked by two brief and successive stimuli delivered from different sensory modalities.