That's interesting. Moving from Southern Europe to Northern Europe that was one of the worst things for me. I simply could not get any sleep. One would think that they would have nice blackout curtains but in fact the curtains let all the light in, making sleeping impossible.
I don't mind the change in light (dark or light) - but a friend recommended sticking alum foil over windows with normal house/floor cleaning soap for glue (doesn't hurt the glass, makes for easy removal).
Worked for me when I worked night shift and went to bed around 10 am.
You need proper blackout curtains where the fabric is in direct contact with the framing of the window. Typically curtains have a lot of space between the fabric and the frame/glass so you'll get a lot of light coming in.
