Sleep forms part of humans' biological need to rest. As a person sleeps, the various physiological processes of a human body figuratively are put into an apparent arrest and some parts of our system that were mostly exploited can be replenished for future use.
However, imagine a system so disrupted that our normal scheduling for sleeping and waking is totally altered. Some people tend to sleep early and wake up early in the morning and some cannot sleep early and as a consequence, wakes up late.
These and other sleep-related problems are manifestations of a malfunctioning biological circadian clock and characterize several forms of Circadian Rhythm Syndrome. Circadian activity is a unique 24-hour period or cycle in which our body is physically patterned.
24-hour vs. 25-hour Cycle
Earth rotates around the sun in a 24-hour cycle, so as our body functions in this 24-hour time schedule. All living organisms subscribe to this cyclic resting and activity pattern so that their body may function in sync with the environment in which they live.
Although humans externally operate under a 24-hour environment, research found that our body clock evidently works significantly different than what we see in the environment.
It shows that the human body closely behaves as if it were under a 25-hour environment. Convincingly, humans reluctance to wake up at a required time and sleeping late at night probably explains this theory.
To compensate for this discrepancy, the body uses time “cues" to effectively counter-manage this asynchronous rhythmical. Setting an alarm helps us wake up at a designated time of the day and allows us to function as if it were under the 24-hour rhythmic schedule.