Day and Night Occurring
The earth is round like a globe. It also revolves around the sun rotating on its tilted axis. This is the reason why the sun rises and appears to be sinking. That is why night and day are made.
The sun shines steadily at one place. The part of the earth that is exposed to the sun is filled with sunlight. The light which falls on the part of the earth, there the day comes out. The part which is hidden behind, has no light. It is considered night there.
The Earth rotates on its axis in 24 hours. This forms night and day. That is, the part of the Earth that faces the Sun, there are days. Likewise, in the rest part, the night occurs. Thus, it is 12 hours a day and 12 hours a night. Seven days are there in a week. The days of the week are also named according to these constellations.