My circadian clock app is for use in research studies examining how diet, exercise and sleep affect health and healing. Our body contains circadian (circa – approximately and dian – day) or 24 h clocks that determines the time to sleep, feel hungry or get ready for physical activity. Research studies run in different locations are trying to understand the interaction between “how much” and “when” we sleep, eat or exercise for better health. You need an activation code from these research studies to download and use the app.