Cycle Day/Night with correct Illumination

I have a 3D game that I make a cycle day/Night, it works perfectly, but the problem I have is with the Illumination. During the day the light is correct, everything looks perfect, but in the night the Illumination is the same, I can see everything perfectly because is a day illumination. I want a dark night with poor illumination. And obviusly that this illumination change during the cycle. I have a variable that marks the time it’s in the game but I don’t what I has to change in the Skylight or DirectionalLight. The shadows are updated according to the time but not the global lighting. Thanks.