I am going to answer you but in doing so I would strongly suggest in the nicest of ways that you take a bit of time to go and do some reading on the basics of growing, this is the best website I've found out there and believe me plenty of others will sell you the same information with a huge less detail and information for a lot of money, so read up and become educated to help yourself. If you are looking to get the most growth potential from a plant you would run it for 6-hours of light, followed by 2-hours of absolute darkness, and then repeat that schedule for the Veg Cycle according to the cannabis industry of commercial growers is what they are claiming is working the best for them. The point of it is like this, are 6-hours of light the plants ability to make the best highest efficiency of the light starts to serious drop off, and a 2-hour break from all spectral colors of light gives it enough time to do it again, giving you the best growth rates.
During the plants life it makes a chemical that is destroyed when the plant is exposed to light, so only when the plant is exposed to a long enough dark period will the plant actually go into flower, so instead of doing the 12/12... you could try a 14-10 cycle of light to darkness, but as you get into the last couple of weeks of flower, go to 12-12 to make sure the plants ripen sooner. When switching from Veg to Flower you can put the plant into 2-3 days of darkness to really force the change into flower and you can do it again at the very end before you cut it down to get the plant to push all of its life into making the buds in a last ditch effort of survival.