Remember why there is a change of day and night on Earth.

Day and night change on Earth due to the fact that our planet revolves on its axis. One of the assumptions why this happened is that even at the beginning of the formation of the Earth, another planet crashed into it, forcing ours to revolve around its axis.

Day on Earth in the part that is turned towards the Sun and vice versa.

The length of the day is not exactly 24 hours, as is commonly believed, but 23 hours 56 minutes 3 seconds. Because of this difference, an additional day appears every four years.