Categories: Circadian rhythm | Hypnotics 

I question the validity of this classification.  A chronobiotic is not the same as a hypnotic.  For delayed sleep phase, for instance, melatonin can act as a mild hypnotic, taken ~1 hour before bedtime.  Or it can be used as a chronobiotic, ~6 hours before bedtime.  Its use as a hypnotic is irrelevant to this article.