First, you need the "Time" (Counter, Value, Sprite with animation, whatever you want).
Then you need a method, to "show" that's night. You can make this with Layout-Effects or a dark layer with changing opacity.
At last you have to say, when it's night (Counter have a special value) - show Night-Layer/special Layout-Effect.
When it's day (...) hide Night-Layer/special Layout-Effect.
Thats the simple answer