Why do we use the a.m.-p.m. system for telling time? The 24-hour day (i.e. 1300 for 1 p.m.) that the military uses seems so much simpler. Do you really think so? I always have to stop and think for a ...

Many people have heard of the circadian rhythms or biological processes that follow a 24-hour cycle. Sleeping at night and being awake during the day is a well-known example of a circadian rhythm.

In addition to 24-hour clocks, mammals and other organisms have 12-hour clocks that are autonomous, work independently from 24-hour clocks and can be modified by external factors. Some bodily ...