NO, it's the 12-1 or gas lamp theory. 12 hours on, then off for 5.5 hours, on for an hour, off for 5.5, and then 12 again, so your only using 13 hours of light time to keep em' in veg. Then in flower, you start at 11/13 and go down half an hour every 2 weeks till you finish at 9 on and 15 off, which is closer to natural light, and it saves on electricity. It supposedly doesn't effect at all, your yield.