Biologic time refers to the rhythm and cycles experienced by living organisms. It is the natural time that dictates sleep and wake cycles, hunger and thirst, and even reproductive cycles. Synonyms for biologic time include circadian rhythm, internal clock, biological clock, and chronobiology. These terms are often used interchangeably in relation to the natural body clock that regulates human behavior and physiology. Other related terms include diurnal rhythm, which describes the 24-hour cycle of the body, and ultradian rhythm, which refers to cycles that occur within the 24-hour cycle, such as the cycles of brain waves during sleep. Understanding biologic time is essential for maintaining health and wellness, as disruptions to natural rhythms can lead to a host of negative consequences for the body and mind.