The clock leaped forward and my lights on was 6am to 6pm. So in the morning I wanted to change, I let the lights come on at their regular time, 7am with the time change. I then adjusted the time on my timer ahead one hour. The result was an 11 hour light period, while the dark was always 12 hours. I would think in the fall you would get one 13 hour day of light, but again, keep the dark at 12 hours. My logic is that the constant 12 hour dark period is the key and that extra or less hour of light isn't a big deal once. Anyway, it seems to have worked for me so far.