Internal Time: Chronotypes, Social Jet Lag, and Why You're So Tired

Internal Time divides the discussion of time into 24 chapters. It presents a number of fictional and semi-factual stories of people in various "odd time" situations as it discusses how time impacts us in our lives. The human clock is almost set to 24 hours. However, there are slight differences, and the body relies on external queues (sunrise) to guide us on the daily schedule. Teenagers tend to arise later, and gradually arise earlier each year until late middle age. (Women actually start this schedule a little ahead of men.) Birds use an internal clock in order to guide their long migrations. Some people may have conditions that cause them to wake up much earlier than normal. Without sensory perceptions, it can be hard to accurately keep track of time.
Time is quite an interesting phenomenon. Mammals may have even evolved to dominate the night (since the air, sea and land were already taken.) Being warm blooded allowed them to be active when other cold blooded animals lacked energy. Later, mammals went back to the day time. However, man was still created innovations like houses and light to continue to dominate the night.