When it is totally dark? just at sunset? It's day 2 of the new pullets in the new coop and I had them inside all night and all day today, opened the coop up in the afternoon. THey didn't come out at all even with treat enticement until nightfall--about an hour before dark. I had to put them back in the coop because they were so active in the run they didn't want to go to bed! THen they were all complaining for a while in the henhouse after that. lots of peeps of frustration!