Are you debating if you should turn the lights on after sunset or before sunrise?

Exactly!

I have read, that I have to turn the light 30 min before dawn and take it for 3 hours. But there was not information about lighting after sunset.

Well I'm not an expert and don't know if there would be difference here between doing it either way, before or after sun time. As long as your plant would get uninterrupted 8 hours of darkness I think it should be fine. I'd probably would start the lights 30 minutes before complete sunset and let them be in the dark for 8.5 hours, and just let the sunrise light be natural without artificial lighting

Also if you do it at end of day it would be a continuation of light intensity and temperature versus starting the day off with high intensity, raising the temperature and than going to natural light low intensity and temp cool down. Besides if I was a plant I'd be pissed if all of a sudden someone woke me up with mid day sun :) instead of gradual increase

I'm still trying to find a definite answer however I believe that first of all it depends on what types of plants you're trying to grow. If the plants need more light intensity than your winter sun can provide than I think you should run the lights in addition to the sun. Here is an interesting article:
http://www.powerplants.com.au/growth-lights/

If you find the answer , let me know , I'm curious

You are right. It depend on type of crop.
I have bumped into very interesting article and according with it lighting schedule for tomatoes has divided into two parts, before sunrise and after sunset.

And I will be very grateful if you live some cooment about the article

Here is a link that might be useful: article

Nice article. What can I say I guess splitting the time works :) And it reinforces the idea that the purpose of using artificial lighting in winter is to match or exceed the intensity of light of what it would normally be in natural season of particular crop in nature under the sun.

Therefore the lights are actually mostly on within the time period of daylight as an addition to sun and few hours added after and before sun time, depending on the plant species of course.

Thanks for the article. I'm currently reading up on CO2 enrichment and this article touched up on it a little bit.