This is called the free-running or Non-24-hour sleep–wake disorder ( non-24 or hypernycthéméral) syndrome, a disorder that causes a chronic sleep trouble provoking a delay or an advance of 1 to 2 hours of the biological clock each day.
Because of this disorder, the circadian clock no longer coincides with the cycle of the day (24 hours), forcing affected people to live on a sleep-wake rhythm longer than day/night cycle.