Hormonal

Evening chronotypes exhibit a significantly delayed subjective sleepiness rhythm (5–9 hours phase shift) compared to morning chronotypes, whereas endogenous circadian markers (core temperature and melatonin) show only a modest 2–3 hour delay, suggesting that subjective alertness drives sleep timing rather than biological phase alone.

If you are an evening type, your biological clock (melatonin/temperature) is only slightly delayed compared to morning people, but your feeling of sleepiness is delayed much more (5-9 hours). This mismatch causes you to stay up late not because your body demands it biologically, but because you don't feel sleepy. To fix this, you must align your bedtime with your biological ability to sleep (temperature/melatonin onset) rather than waiting until you feel subjectively sleepy, which happens too late for healthy sleep duration.