I have lights in my chicken sheds over winter, is on a timer and goes on at 6am until about 8, then again from 4pm until 8pm. They do lay through the winter, but I don't do it to the ones who are in their first winter. Mine are about 18 weeks now and have not started laying, so i don't hold many hopes for them, but the older batch is still laying. although they are now going into their third winter eggs are down a bit.