Day

A day is the time period of a full rotation of the Earth with respect to the Sun. On average, this is 24 hours (86,400 seconds). As a day passes at a given location it experiences morning, afternoon, evening, and night. This daily cycle drives circadian rhythms in many organisms, which are vital to many life processes.

thumb|Hemera (1884) by William-Adolphe Bouguereau

calculation of elapsed time by the apparent position of the sun

thumb|right|Steppe eagles are diurnal, and hunt during the day. thumb|right|Humans are diurnal, and organize their work and [[business mainly in the day.]] Diurnality is a form of plant and animal behavior characterized by activity during daytime, with a period of sleeping or other inactivity at night. The common adjective used for daytime activity is "diurnal". The timing of activity by an animal depends on a variety of environmental factors such as the temperature, the ability to gather food by sight, the risk of predation, and the time of year. Diurnality is a cycle of activity within a 24-

thumb|260px|Dagr (1874) by Peter Nicolai Arbo Dagr (Old Norse 'day') is the divine personification of the day in Norse mythology. He appears in the Poetic Edda, compiled in the 13th century from earlier traditional sources, and the Prose Edda, written in the 13th century by Snorri Sturluson. In both sources, Dagr is stated to be the son of the god Dellingr and is associated with the bright-maned horse Skinfaxi, who "draw[s] day to mankind". Depending on manuscript variation, the Prose Edda adds that Dagr is either Dellingr's son by Nótt, the personified night, or Jörð, the personified Earth. O

the eighth day after a religious feast, or the whole 8-day period within

pattern that recurs every 24 hours as a result of one full rotation of the Earth with respect to the Sun

personification of day, and the Roman counterpart of the Greek goddess Hemera

short-term changes in the length of the day