Lighting in vray

Hello guys
Could anyone help me find out what my problem is about Night light?
I mean, for example I want the sun light to come to the interior scene around 7 pm…
I have removed Vray sun and I have replaced it with Rhino sun ( as I saw in a webinar) and then I set it manually almost at the time that I wanted. Then in vray environment setting and also background setting I chose texsky and Rhino sun.
Then I set their setting to pretham et al. I changed the shutter speed (in camera part) to 400 and after that I put a rectangular light in my interior scene.
After I push the render button the result of it , is a bright scene just like a day time!!!
what should I do to get Night light? Could you please help me to find out?