Exactly that. She had a small room with velux window and we had a black out blind made. Even though it always let in some light, the room was always dusky in the day. Since I trained the life out of her to sleep in the day in her cot - which she did, brilliantly - she obviously grew used to darkness.
7 months later. We've moved house. We're currently in limbo as wait for house to complete and past two days she's cried A LOT being put down. Can't decide if she's just teething bad (she's become VERY whingy generally) or whether it's because the room she's now in is much brighter.
We put up a travel black out blind and ten minutes she was no longer crying, but babbling and self-settling.
So. My point is: have we messed up massively by using one? Rod. For. Own. Back scenario...