disorder in which the major sleep episode is advanced in relation to the desired clocktime, that results in symptoms of compelling evening sleepiness, an early sleep onset, and an awakening that is earlier than desired. This is classified as a circadian rhythm disorder. The sleep phase occurs well ahead of the conventional bedtime and the tendency is to wake up too early. The major complaint may concern either the inability to stay awake in the evening, or early morning awakening insomnia, or both.