A novel theory of time discounting is proposed in which future consumption is less valuable than present consumption because of waiting costs. Waiting is intermittent as consumer's attention is periodically distracted away from future gratifications. A new axiom is introduced, called weak impatience, according to which consumers are impatient only if they pay attention to the good in the present, or when all options are in the future, a strictly positive probability exists they will pay attention to it. The model unifies and reinterprets three empirically relevant properties of intertemporal preference: decreasing impatience, present bias and sub-additive discounting. In addition, the model predicts new testable behavioral patterns, not predicted by other discounting models.