Dd's 3 now. As a small baby she always woke at sunrise, no matter when that was, so, being broke at the time, I covered her windows with blackout material which has been a lifesaver.
But, as dp points out unless we want her to think people all have dark bedrooms it's probably a good idea to give her back some light! (we're not cruel by the way, she spends no time in her room apart from sleeping, it's a tiny room)
When did you give up on blackouts and feel fairly confident your child wouldn't wake at the crack of dawn?