Ironically, there is a thread right above this one with the same subject. Here's what I just wrote there:
When I started out with chickens, I didn't even know that there was such a thing as a timer and kept light on my birds 24/7. I never had a single problem. Then I found that I could buy a timer for like $5 at
WalMart - so I did. I now keep my birds on 15 hours of light and still have had no problems whatsoever.
All the arguments I've read for not adding supplemental light have centered around the idea of letting the birds have some rest. My response to that is to simply point out that anyone who's had chickens for any time at all has seen birds sitting outside perched on a limb or on the ground in the middle of the day, in the middle of summer, with nothing but sunlight around them, and be sound asleep. And anyone who's had chicks has seen the little potlickers be scooting hither and thither only to stop all of the sudden and fall over like they're dead but rather just go sound asleep.
As for letting nature take its course, since when do any of us do that? I don't know anyone that lets their birds totally fend for themself. We provide them with special foods, shelter, vitamin supplements, worming and parasite treatments, etc. etc.
My birds must pay for themselves. There is no free-lunch on my place. So to have them out of commission for months during the Fall, Winter, and Spring just doesn't make any sense at all to me. If others want to do that and/or can afford to do that, I say God Bless them but it doesn't happen here. Besides that, I've got folks who have come to rely on me to provide them with farm fresh eggs. I'd never keep any of them coming back if I went out of production for half a year.
Lastly, interestingly enough, I've got some ducks still in a pen down by the pond because they haven't stopped laying. Last year I got duck eggs all through the winter and they aren't on any lights other than the utility line that is up in our driveway.
Cackler, as for what is the best time to set the lights to come on and go off, I say do what works best for you. I have my lights coming on at 0430 and off again at 0730. Then they come on again at 1800 and go off at 2100. I go out about 2045 to do my chores. When the light goes off I go in the coop, pull all the birds out of the nesting boxes that habitually want to spend the night in them and put them on the roost. That way I don't have a bunch of filthy eggs every morning. And btw, when I set my clocks back in the house, I didn't bother changing the timer outside at all.
Hope that helps.
God Bless,