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 individuals' attention is periodically distracted away from future gratifications. The more individuals expect to pay attention to the reward, the more they are impatient. The model revisits the fundamental link between short and long-term impatience and solves two behavioral anomalies: impatience over short durations and sub-additive discounting.