how do people get tired when they have a early night?

Question: how do people get tired when they have a early night?
- Keywords:
  sleep,
  tired
Asked by RonnieTheStar to Jimi on 17 Mar 2016.
- Jimi Wills answered on 17 Mar 2016:
  
  changes to you sleeping habits can interrupt your sleep…
  
  also, you might be waking up durnig a different phase of sleep from normal (if you have VERY regular sleep patterns)

Question: how do people get tired when they have a early night?