Many of my friends grow on the calender. The know their strain, and give or take 2 or 3 days, they know when their plants will be ready.
The only thing that takes more or less time are their clones. Not all of them get roots at the same time or develop in the same way. But after a few weeks of veg and they think when they are ready, they flip the clock.
Their rooms always have the same temperatures and humidity.
Those strains are for example Super Silver Haze. 9.5 to 10 weeks.
But I am wondering if there is a strain that can do it in 8 weeks.