The skin is now recognized as an active peripheral circadian organ that both reflects and regulates the body’s 24 hr physiological rhythms. Endogenous molecular clocks within keratinocytes, melanocytes, fibroblasts, and immune cells coordinate gene expression, proliferation, and repair to maintain cutaneous homeostasis. This review synthesizes recent advances linking the core circadian network (CLOCK-BMAL1, PER/CRY, and ROR/ REV-ERB loops) to fundamental skin functions-including barrier renewal, pigmentation, immune surveillance, and wound healing. Emerging evidence reveals reciprocal signaling between the central suprachiasmatic nucleus (SCN) and cutaneous clocks, integrating systemic hormonal and metabolic cues with local circadian outputs. We further examine how clock disruption contributes to dermatological disorders such as atopic dermatitis, psoriasis, and melanoma, and highlight therapeutic and cosmetic strategies that align interventions with biological time. Collectively, these insights establish temporal regulation as a fundamental dimension of skin biology and a promising framework for time- based precision dermatology.