how to end with 12 12 I choose

[DogtowN]

OK so I want to have my lights on from 7:30 to 7:30 as my 12 ,12 what hours would I pick for 18 on- do I cut the 6 hours from the front, back or split the time

Huh, never gave it much thought, but I normally add the 6 hours of dark time while keeping "sunset" the same.

I doubt that it matters much how you make the transition, really. People use so many different schedules for veg, and use varying lengths of initial darkness to enter flowering, too. You have to take care when adjusting the schedule during flowering, but the transition isn't super critical.