How to make Scene darker to look more like night time.

Hey there guys, with my scene it has a day and night cycle, but the night time is terrible, it stays as light as day time, with a black sky and objects remain the same, how can i make everything darker to make lights and everythings else more effective and elusive?

Day Time

Night Time

As you can see the only thing that changes is the sun beams and the black sky, but objects remain the same.