what is a length of a day
A day is a unit of time. In common usage, it is an interval equal to 24 hours. It also can mean the consecutive period of time during which the Sun is above the horizon, also known as daytime. The period of time during which the Earth completes one rotation with respect to the Sun is called a solar day.his phenomenon is due to tides raised by the Moon which slow Earth's rotation. Because of the way the second is defined, the mean length of a day is now about 86 400.002 seconds, and is increasing by about 1.7 milliseconds per century (an average over the last 2 700 years).