To start with the information found about strains on seedbanks is the breeders description not that of the seedbank. Next those are at best estimates because conditions are different from grow room to grow room and in the case of outdoors just a few miles farther north or south can make a difference in things so they really can’t get any closer to being accurate.
 
Look at the number of weeks or days the breeder information says about the strain of theirs you purchased and then when you get to about a week before the earliest finishing date, going by the breeder information, begin looking at your trichomes and check what their color is. Check on the top of your plants, in the middle of your plants and at the bottoms of your plants and when the trichome color will give you the high or the body stone or the combination of each that you most want, need or enjoy that is when you harvest regardless of what number of weeks or days have passed since flowering began.
 
Harvest according to trichome color and according to trichome color alone.