Daytime

For other uses, see Daytime (disambiguation).

"Length of day" redirects here and is not to be confused with Day length fluctuations.

Sunrise in Brisbane Water National Park, Australia

A daytime sky with white clouds

Daytime or day as observed on Earth is the period of the day during which a given location experiences natural illumination from direct sunlight. Daytime occurs when the Sun appears above the local horizon, that is, anywhere on the globe's hemisphere facing the Sun. In direct sunlight the movement of the sun can be recorded and observed using a sundial that casts a shadow that slowly moves during the day. Other planets and natural satellites that rotate relative to a luminous primary body, such as a local star, also experience daytime, but this article primarily discusses daytime on Earth.

Very broadly, most humans tend to be awake during some of the daytime period at their location, and asleep during some of the night period.

Characteristics

Approximately half of Earth is illuminated at any time by the Sun.

Daytime length variations with latitude and seasons

See also: Sun path

Day length as a function of latitude and the day of the year. Latitude 40° N (approximately New York City, Madrid and Beijing) is highlighted as an example.

A plot of hours of daylight as a function of the date for changing latitudes. This plot was created using the simple sunrise equation, approximating the sun as a single point and does not take into account effects caused by the atmosphere or the diameter of the sun.

Earth daylight on the June solstice

Earth daylight on the December solstice

At middle latitudes

An approximation to the monthly change can be obtained from the rule of twelfths.

See also

• Daylight saving time
• Solar eclipse
• Sunrise equation
• Sunshine duration