have to disagree. most people count flowering from the very first day the plant is showing sex. the reason behind it is that sometimes it takes 10 days (as you mentioned), sometimes less. so when you count from signs of sex everybody knows whats going on regardless when u switched to 12/12. i did 36hrs darkness period before 12/12 and one plant showed signs of malesness right afterThe flowering period starts when you start the 12/12 light cycle. The plant will show sex at the earliest 10 days.
First the plant aint stretching.the plant had preflowers before 12 12.just two weeks makes a big difference right at the end of flowering time me and my buddy been arguing about this.I say it shouldn't start until it starts flowering buddy says different though.idk.your plant should b showing sex before u flower ideally, if u force flower before your plant is showing sex in VEG then it is not mature enough to bloom. And i always start counting my flowering days from the onset of flowers, if yr plant is just stretching for two weeks before it produces flowers its not flowering is it? and ive had plants that have started to flower in just 7days of 12/12