Growing indoors, you have a seed they say takes 8 weeks of flower. Is that 8 weeks from the time you flip the lights to 12/12, or from the time the plant shows the first signs of flower.
Typical transition is 10 to 14 days then start counting flower time.
Welcome to the community . 
It would be 8 weeks from flip. Its the only constant. Unfortunately, some phenos can go alot longer. Ive seen 8wk plants take 12. Luck of the draw.
Welcome to the fourm @stonepeace
Photo or Auto?
Plan on at least 10 weeks. I’ve noticed over the years that it always takes two weeks longer than they say, so basically start counting when you have actual budlets.