it depends on your expectations. chances are though you'll get a little tiny sucker size bud at the top, and thats it.
18-24 hours, and you can change it right now even, will put them into a veg state, they'll get taller, bushier, let them mature a bit for a better harvest/development. ..and you decide when to change the light to 12/12 again to initiate flower. google grow bible quick though, before you kill her and read it too.
who told you to grow these at 12/12 ?