Local jurisdictions can impose city and municipal ordinances that set curfews for minors.  If you were a minor and out after your city's curfew, then the police could detain you and call your parents because of the curfrew violations.If you were not a minor, but looked very young, then the police could detain you just to make sure that you were not underaged.On the flip side, if you clearly were not a minor, then the only thing law enforcement could do is simply talk to you.  Law enforcement can talk to anyone at any time.  However, they cannot detail you unless they have a reason to believe that you are committing some offense.