What does the flowering time of a strain actually mean?

Hello ladies and gents,

I have a question for you all, what does the flowering time mean exactly? If a strain has a 7-8 week flowering time does that mean that it will be done and ready for harvest by 8 weeks FROM THE DAY YOU CHANGE TO 12/12? Or does it mean that after you see results from changing to 12/12 it is 7-8 weeks from that point forward?

It seems as if every harvest out of all the strains ive grown (roughly 11 different strains) never seem to be done by the point they are supposed to? So far I have only done out door crops and am budding my first indoor crop so we'll see how that goes but all the harvested crops have been at least 2 weeks later than the predicted bud time? I have done clones and seeds so i know the information (flowering time) wasnt always wrong. Is there anything that is known to slow down flowering time? i.e. high temps/cold temps etc? I live in a fairly hot area and the summers get into the low hundreds quite often, which is when my plants usually start to flower.

Thanks in advance for the help guys.

from the time you change to 12/12 it will take 7-8 weeks to finish flowering in a typical strain.

the time is ioven considering a lot of light and perfect conditions

there are a lot of things that will influence flowering time, so it's more a rough guideline. Figure that's what the breeder experienced on average. Don't expect it to be spot on your experience, and by all means, put to use methods to determine ripeness, like magnified trichs...

The flowering starts from 12/12.

It's a rough estimate.