Answer:
Circadian rhythm
Explanation:
The condition given in question statement is called circadian rhythm.
Circadian rhythms are the changes that develop in humans across the day cycle and it basically responds to the light and darkness. One of the very examples of this is sleep, naturally humans tend to sleep at night while they get up in the morning or light. However the sleep timings or all the people are not same, it can differ in people also and this is not an abnormal feature