List of United States Presidents by military rank. The United States Constitution names the President of the United States the Commander-in-Chief of the U.S. armed forces. Many Presidents, however, also served in the military before taking office; all but 12 of 43 served. 1  1 Table of United States Presidents by military rank.  1.1 General of the Armies.
It is called circadian rhythms. Humans tend to sleep when it is dark out. I, on the other hand must work all night and sleep in the day. so my natural rhythms are screwed up. Being bored makes us sleepy, reading and watching TV makes me sleepy also physical tiredness.
Healthy Sleep Habits. Your behaviors can have a major impact on your sleep and can contribute to sleeplessness. Your actions during the day, and especially before bedtime, can make it difficult to fall asleep, stay asleep or get restful sleep.