Unscientifically....with a small sample of on 5x...my plants have had less stress and shown better transition from 24 hours to 12/12, with three days of darkness between. (72 hours, plus or minus).



Although variability always exists....

-it could be I've been better at temp/nut management
- it could be different strains....

But I just did this...just took a pair of ladies out of darkness and I was pleasantly surprised they looked more vibrant and healthy after dark phase than before....

So your call. But day 1 into darkness =day one into Flower...by my count