The human circadian clock ensures that biochemical and physiological processes occur at the optimal time of day. In addition to a central pacemaker in the body, recent evidence suggests that peripheral mammalian tissues also possess autonomous circadian oscillators, which are regulated by genes linked to distinct tissue-specific functions. The skin is situated in a position naturally exposed to diurnal environmental changes. The skin's chronobiological functioning influences skin aging, cell repair and development of skin cancers, as well as optimal timing of drug delivery to the skin. An understanding of circadian skin-related functions and the impact of their disruption allow clinicians to improve therapeutic decision-making and maximize the effectiveness of prescribed treatments.