I have noticed that when loading, sometimes the lighting does move as the sun would move through the sky and there is night in the game already. I really hope it is something that was not ready for EA, I fully expect there to be a day/night cycle.
Don't you play co-op together? so the time of day would be the same?
Also, again, I'd like to mention that fire looks great at night and Larian is really missing out on fire if they miss out on fire at night. Just gonna leave that here...