Is it possible to make an interior NOT adjust brightness with time of day? I made a custom home with no windows and there is no earthly reason that it should be so bright during the day and pitch black at night. I've asked on many different sites and no one seems to know so this is my last hope!

Check your cell lighting data. You may have enabled the sky options.

I thought that too initially, I actually have sky disabled though. I'm really not sure where else to look!