My understanding is that you need to maintain 14 or 15 solid hours of light (with a lightbulb in the winter) to continue to get your chickens to lay through the winter.
Apparently some breeds may lay through the winter even without artificial light but their production goes down. Most breeds quit laying altogether during the winter.
I do know that you need to have the lights turn on in the wee morning hours and go off before sundown. That way the chickens will still be able to find their roosts for the night. If you have a lightbulb on after dark and it suddenly goes off - the chickens can literally get lost and not be able to find their way back into the hen house and their roosts.
You need to continually adjust the lights to maintain that 14 or 15 hours of daylight. I was told that if the light goes off, even for an hour or so, in the dark that the chickens may quit laying or go into a molt!
Since I am a newbie there are people here that can correct me if I'm wrong or give better information.