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.
If you go to bed at the same time each day, your body will quickly adapt and help you fall asleep at that time each and every night. This same thing happens if you wake up at the same time each day, as you body will adapt to become tired when 7-8 hours before it expects to wake up the next morning.