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.
因为主段有足够的时间来完成充满SWS的睡眠周期，主段睡眠在夜间进行为佳。对大多数人来说，由于各种社会义务，主段也比较容易安排在晚上。小睡则在白天进行为佳，因为更深的睡眠阶段不太可能出现。在适应之后，小睡可以相对有弹性，而主段则更难移动。
