In a similar threads, we have been discussing flowering time claims & when to start counting days when budding. Here's a microcosm of our discussions.
42-45 days is as short as it gets for fully developed trichomes. Not to say that is Gospel, but no one has stepped forward with proof of a shorter timed variety.
We have decided that indoors the day the flip is switched is day 1 of flowering. That's due to the fact we all do it, that is, flip the switch. Outdoors, budding begins when the plant flips the switch & it is difficult to tell when that is, so looking for flowers forming is the best case scenario. Begin counting days when you see flowers appear outdoors.
This may help to account for the differences we see in claimed flowering times. Myself, I tend to use the bigger number I see. For example, a 45-55 day bloomer, like the Blue Dynamite I am currently running. I use the 55 number & seriously begin checking trichomes @ that time. Most claims for blooming times are under optimum conditions @ best & @ worst are just downright fabrications or marketing ploys.