We often assume that our ancestors went to bed ‘naturally’ when darkness fell and rose with the Sun. However, sleep times have never been such a simple matter, whether in Japan or elsewhere. Even before the invention of electric light, the documentary evidence shows that people were scolded for staying up late at night for chatting, drinking and other forms of pleasure. However, scholars – particularly young samurai – were considered highly virtuous if they interrupted their sleep to study, even though this practice may not have been very efficient as it required oil for their lamps and often resulted in them falling asleep during lectures.