Complex sentence: In chronotherapy an attempt is made to move bedtime and rising time later and later each day, around the clock, until these times reach the the number of hours of sleep per night an individual needs to be fully functional.
Split into simpler sentences: In chronotherapy an attempt is made to move bedtime and rising time later and later each day, around the clock, until these times reach the desired goal. The desired goal is the number of hours per night an individual needs to be fully functional.