there was a really incredible grower here a while back and i wont mention his name, but JM was his initials and he always said he starts counting 7 days after flip

(which is about the time you start seeing actual flower)

day one of flower is when you first see flower. Hence the name!

sorry to be kinda blunt!  

Brutally honest?  ...I totally agree...in my experience that's anywhere from 7 to 14 days after the light flip depending on the  strain...