Core sleeps are favoured during night time, as they allow sufficient time to complete SWS-filled sleep cycles. They are also easier to schedule at night for most people due to social obligations. Naps are favoured in the day, since deeper sleep stages are less likely to appear then. After adaptation, naps can be relatively flexible, whereas cores are much harder to move.
因為主段有足夠的時間來完成充滿SWS的睡眠週期，主段睡眠在夜間進行爲佳。對大多數人來說，由於各種社會義務，主段也比較容易安排在晚上。小睡則在白天進行爲佳，因為更深的睡眠階段不太可能出現。在適應之後，小睡可以相對有彈性，而主段則更難移動。
