Night and Day

Night or nighttime (sp. night-time or night time) is the period of ambient darkness from sunset to sunrise in each twenty-four hours, when the Sun is below the horizon. The exact time when night begins and ends (equally true with evening) depends on the location and varies throughout the year.
A day is approximately the period of time during which the Earth completes one rotation around its axis. A solar day is the length of time which elapses between the Sun reaching its highest point in the sky two consecutive times.