Circadian Rhythm Disorder is a mismatch between the body's internal clock and the external 24-hour schedule.Quoted From: https://www.emeraldsleep.com/common-sleep-disorders/circadian-rhythm-disorders.html
"One fourth of all chronic sleep disorders are the result of a mismatch between the body"s internal clock and the external 24-hour schedule. These sleep-timing problems are called circadian rhythm sleep disorders because "circadian" describes the body"s daily sleep/wake hormone regulation (Circadian is Latin for "about a day"). In addition, most other sleep disorders can damage circadian rhythms and further compound the sleep problem. The National Institute of Health estimates that over 35 million Americans suffer from circadian rhythm disorders."