section_path: Boundaries
section_name: Boundaries
paragraph_text: Boundaries
  
  For most diurnal animals, the day naturally begins at dawn and ends at sunset. Humans, with their cultural norms and scientific knowledge, have employed several different conceptions of the day's boundaries.
  
  In the Hebrew Bible, Genesis 1:5 defines a day in terms of "evening" and "morning" before recounting the creation of the Sun to illuminate it: "And God called the light Day, and the darkness he called Night. And the evening and the morning were the first day."The Jewish day begins at either sunset or nightfall (when three second- magnitude stars appear). Medieval Europe also followed this tradition, known as Florentine reckoning: In this system, a reference like "two hours into the day" meant two hours after sunset and thus times during the evening need to be shifted back one calendar day in modern reckoning.Days such as Christmas Eve, Halloween (“All Hallows’ Eve”), and the Eve of Saint Agnes are remnants of the older pattern when holidays began during the prior evening.
  
  The common convention among the ancient Romans, ancient Chinese and in modern times is for the civil day to begin at midnight, i.e. 00:00, and to last a full 24 hours until 24:00, i.e. 00:00 of the next day.
  
  In ancient Egypt the day was reckoned from sunrise to sunrise.
  
  Prior to 1926, Turkey had two time systems: Turkish, counting the hours from sunset, and French, counting the hours from midnight.