Ok, if you really want to imitate nature here is what you can try. Its a pain in the ass unless you have a timer that can do it. When plants start growing in the spring, the days are still relatively short. Go back over the last year and research the sunrise and sunset times. Starting at the beginning of the grow apply the daylight time each day as it would out side. That means every day you will have to increase the daylight time by a minute or so until it is time to start decreasing the minutes per day. I thought about trying this but decided against it, I am not going to get in there and start screwing around with the timer everyday. There is a system for this made for aquariums, however it bases its schedule off of the moon phases.