Regardless of the season, my hens all head back to the coop 20-minutes before full dark and I lock them in shortly thereafter. At this time of year they're in the coop by 8:40 and settled on their roosts by 8:50. During the months of early darkness they come inside 20-minutes before dark then mill around inside the coop, take dust baths, eat, etc. until the coop lights begin to dim around 8:30. Their routine stays much the same year round, but they spend a lot more time inside the coop during the colder, darker months.