It is appropriate to have more than four hours of deep sleep per day, so it is recommended to ensure at least 6-8 hours of sleep per day for adults, 8-10 hours for adolescents, and more than 10 hours for children. So it is recommended that normal adults, adolescents and children should go to sleep before 22:00, because the body has to enter a light sleep time before entering a deep sleep. Usually it takes about three hours of light sleep phase before it can gradually enter the deep sleep phase. So after entering the light sleep at 22:00, usually after 3-4 hours of circulation, you can enter the deep sleep at about 2:00 in the morning. And the daily deep sleep time is controlled at about 2:00 am, so as to meet the body’s circadian rhythm and the quality of rest and sleep.