Why if I go to sleep at 12:00 am and 1 am I feel tired the next day even when I sleep 8 hours?
To be honest, not everything I give you is a checked scientific fact, but most are commonly known facts and some are experience-based opinions.First of all, most of what you need to know is in the other answers.Now to state my answer:1- It is a commonly believed concept that the first hours of the night, namely 10 pm - 1 am, are the hours when your body normally achieves best rest and your brain achieves best organization and repair. "Normally" because like the others have stated, your body can learn and adapt to different habits and make them a new norm.Therefore, sleeping later than 12 am would deprive your body of 2 earlier most efficient sleeping hours it is routinely used to.2- No judgements, but people most often stay up late on electronic devices (TV, computers, smartphones, etc.)These devices, through their screen brightness and through electromagnetic waves, act as stimulants for your brain; they make it unlikely to doze off or sleep for some period of time (minutes).If spend your late nights away from screens and phones in general, this won't be a problem.3- Like most of the others told you, your body gets used to a certain rhythm of day-night-day-night and wake-sleep-wake-sleep. So it will take some time (a few days at least) to get your body used to different sleeping hours. One method of overcoming this could be taking Melatonin (sleep hormone) tablets before sleeping at any time different than your routine. It basically fools your body into believing it's the usual sleep time. This is frequently used to overcome jet lag, which is caused by a similar issue.Hope I helped.