Historian A. Roger Ekirch thinks that the traditional pattern of "segmented sleep," as it is called, began to disappear among the urban upper class in Europe in the late 17th century and the change spread over the next 200 years; by the 1920s "the idea of a first and second sleep had receded entirely from our social consciousness." Ekirch attributes the change to increases in "street lighting, domestic lighting and a surge in coffee houses," which slowly made nighttime a legitimate time for activity, decreasing the time available for rest. Today in most societies people sleep during the night, but in very hot climates they may sleep during the day.Huntington, Ellsworth (1915) Civilization and Climate . Yale University Press. p. 126 During Ramadan, many Muslims sleep during the day rather than at night.
Historian A Roger Ekirch thinks that the traditional pattern of "segmented sleep" as it is called began to disappear among the urban upper class in Europe in the late 17th century and the change spread over the next 200 years; by the 1920s "the idea of a first and second sleep had receded entirely from our social consciousness" Ekirch attributes the change to increases in "street lighting domestic lighting and a surge in coffee houses" which slowly made nighttime a legitimate time for activity decreasing the time available for rest Today in most societies people sleep during the night but in very hot climates they may sleep during the dayHuntington Ellsworth (1915) Civilization and Climate  Yale University Press p 126 During Ramadan many Muslims sleep during the day rather than at night