daytime

Daytime is the portion of the 24-hour cycle during which the Sun is above the local horizon. In everyday usage it roughly corresponds to daylight hours from sunrise to sunset, when the sky is illuminated and shadows are cast. Astronomical definitions distinguish daytime as the interval when the Sun is above the horizon, with twilight periods (civil, nautical, and astronomical) defined separately for times when the Sun is below the horizon but still above certain solar angles.

Day length varies with latitude and season due to the tilt of the Earth's axis relative to its orbit around the Sun. Near the equator, day and night are nearly equal year-round, while higher latitudes experience longer days in summer and shorter days in winter. In polar regions, extended periods of daylight can occur around the summer solstice (the midnight sun), or extended darkness around the winter solstice (polar night).

Temporal markers associated with daytime include sunrise, solar noon, and sunset. The Sun’s position is affected by atmospheric refraction, which causes the Sun to appear above the horizon slightly before geometric sunrise and after geometric sunset. Timekeeping practices such as daylight saving time and the use of time zones can shift clock time relative to solar time.

Daytime influences many aspects of life, including visual activity, opportunities for outdoor work and recreation, and ecological processes such as photosynthesis. Cultural, economic, and religious activities are often structured around daytime hours and their natural variations.