Tired, but not ready for bed?
Time awake is only part of the story. Your body clock also helps decide when you feel alert and when you are ready to sleep.
Your clock takes cues from the world.
A rhythm of roughly 24 hours.
The central clock in your brain helps coordinate daily timing. Light reaching your eyes is an important signal that connects it to the outside day.
Open a moment in the day.
Daylight
Light helps set the timing system and can promote alertness. Daylight exposure is one cue that keeps the body connected to the daily cycle.
Evening
As biological night approaches, melatonin usually rises. Bright light late in the evening can delay that signal; routines and individual timing also matter.
A different schedule
Shift work and travel can put the external schedule out of step with internal timing. Being tired does not always make it easy to sleep at a new time.
After a long flight, Jo feels exhausted but wide awake at local bedtime. What could be happening?
Read the explanation
Jet lag can leave your internal timing out of step with the local day, even when sleep pressure is high. These are two interacting systems, not one switch.
People do not all keep the same clock.
Some people naturally prefer earlier sleep; others prefer later sleep. Teenagers often shift later, while older adults may feel sleepy and wake earlier.
A predictable sleep schedule and time outdoors in daylight can support daily timing. If shift work or persistent sleep problems make that difficult, discuss your circumstances with a clinician rather than forcing a one-size-fits-all timetable.