I'm surprised nobody has mentioned GLR. Which is the Gas Lantern Routine and the Veg schedule is as follows: 12 hours on, 5.5 hours off, 1 hour on, 5.5 hours off. When you are ready to flower just remove the 1 hour nightly interrupt and run 12 on/12 off.
Here's some of the many benefits of running this schedule. Plants build up hormone levels to the brink of flower. The nightly interrupt is the only thing keeping them from flowering on their own schedule. Plants will grow tighter nodes and be less leggy during veg. You won't get any pre flowers unless it's a genetic issue which this light schedule helps identify.
Once the interrupt is removed plants will barely stretch because their hormones are already built up to the point of flower. They focus their energy on flower and resin production immediately rather then stretching for two weeks which can be problematic indoors.
Plants take a certain number of light hours to complete their life cycle. When you reduce the daily light hours your plants will grow slower in return. The way I offset this is I start seedlings sooner in my nursery under less lights and I transplant them into the main room once their established. Overall this helps me save energy and maximize my indoor ceiling space. I've grown many tall sativas with this light schedule where it would otherwise be impossible.
Here's some photos of indicas and sativas from seed flowered at 12 / 12 and vegged in Gas Lantern Routine.