Non-24-hour sleep–wake disorder

Non-24-hour sleep–wake disorder (non-24, N24SWD, or N24) is one of several chronic circadian rhythm sleep disorders (CRSDs). It is defined as a "chronic steady pattern comprising [...] daily delays in sleep onset and wake times in an individual living in a society".

Source: Wikipedia — Non-24-hour sleep–wake disorder (CC BY-SA 4.0)