Consumers often make decisions about outcomes and events that occur over time. This research examines consumers' sensitivity to the prospective duration relevant to their decisions and the implications of such sensitivity for intertemporal trade-offs, especially the degree of present bias (i.e., hyperbolic discounting). The authors show that participants' subjective perceptions of prospective duration are not sufficiently sensitive to changes in objective duration and are nonlinear and concave in objective time, consistent with psychophysical principles. More important, this lack of sensitivity can explain hyperbolic discounting. The results replicate standard hyperbolic discounting effects with respect to objective time but show a relatively constant rate of discounting with respect to subjective time perceptions. The results are replicated between subjects (Experiment 1) and within subjects (Experiments 2), with multiple time horizons and multiple descriptors, and with different measurement orders. Furthermore, the authors show that when duration is primed, subjective time perception is altered (Experiment 4) and hyperbolic discounting is reduced (Experiment 3).