it triggers a hormonal balance shift inside the plant...
This is why it is a 'dark-dependent' plant... i think they've changed teh terminology ("long-night"?) in the last 40 years, but still means the same thing... don't interrupt the dark period! You could fuck up the hormonal balance shift that triggers flower production. it shifts gears of production.... and, unlike what most believe, the plant still requires mostly the same level of nutrients. this is why you see so many burnt up plants of ppl that follow the groupthink that says otherwise.... but, they know it's better because they never compared to a control group and their ego wouldn't allow anything else anyway lol.... wouldn't want to test it properly and find out a totaly uneducated guess was wrong, Bwahaha.
www.youtube.com/watch
7 nanomoles of light per second is enough to cause problems in a marijuana plant. Yes, the moon is less than that.
So, 7-14 days you'll see some preflowers. These can actually present in more mature vegetative plants, but flipping to 12/12 will cause them to grow, if they have not yet. Vegetative growth continues for 3-5 weeks after the flip even as buds start to form at nodes and then start to stack up. When stem elongation and leaf growth stops, you know it is 100% bloom phase.