I use two schedules only. 18/6 and 12/12. Nothing inbetween. No dark periods, no coddling or aclimating...nada.

Be aware, too...darkness may be something that some folks claim works. But in my garden...there is no need to add stress during puberty.

Plus, it's easier. Two rooms. One on 18/6, one on 12/12. At any point you decide...you can move plants from veg to flower. If sexing, you can at any point return them to 18/6. And there's no need to change the timers. (unless your area observes daylight savings time)