The correct answer is it starts when you see pistils, think about it, when is the flip on an outside grow? Can you pin point the time of the flip outside? No it depends on where your growing, so how can there be one answer from the breeder?

That said, and as RbtAsq said, we cant always pin point when a plant started making flowers so the flip is an easily definable X on a calendar. Also I want to have a ball park idea when my next 2 grows will begin and end so I start the count from the flip and add 2-3 weeks to the estimated flowering time.

The fun part of this is it annoys RbtAsq a little when I am right. LMAO