Days
A day is a basic unit of time defined by the rotation of the Earth relative to the Sun or to distant stars. In civil use, a day is 24 hours long, subdivided into 24 hours, 60 minutes per hour, and 60 seconds per minute. There are several technical definitions: the solar day, which is the interval between successive noons and is close to 24 hours; the mean solar day, the average length of solar days; and the sidereal day, the time for Earth to complete one rotation relative to the stars, about 23 hours 56 minutes.
Historically, days were anchored to the day-night cycle. Modern timekeeping relies on Coordinated Universal Time (UTC)
The term day can also refer to a date within a calendar, such as Monday, 1 January.
The names of the days of the week in many languages reflect a mix of astronomical and
On other planets, the length of a day differs widely: Venus has a sidereal day of about