When night comes, it covers the earth with its darkness, Allah (swt) says:

 {يُغْشِي اللَّيْلَ النَّهَارَ يَطْلُبُهُ حَثِيثًا }

(He covers the night with the day, [another night] chasing it rapidly;) (Al-A’raaf: 54)

Even though, sometimes, it seems that there is opposition between day and night, in fact, there is not any, rather, there are cooperation and integration between them in the universe, since, movement of day is generated from the night, and rest of the night is generated from the day.