Part One of the series "Time: The Story of Existence." Where does our sense of time passing come from? Besides breathing and heartbeat, does the human body have another source of internal rhythm? Illustrates that scientists have discovered a stopwatch within the brain that regulates body chemistry and gives us our awareness of time. Host Michio Kaku interviews the geologist who first theorized the existence of the internal clock while in subterranean isolation, monitors an experiment that reveals time distortion experienced during trauma, meets a father and daughter who (due to a rare genetic disorder) have body clocks that run too fast, and visits a captive gorilla with a rudimentary sense of time. Original BBC title: "Daytime." Accessibility options on the DVD are: (1) audio description, (2) expanded description, (3) subtitles for the deaf and hard of hearing.