Autoflower plants change from the vegetative to flowering state with age, not the changing of their light cycle. They have a short grow-to-harvest time and can be ready to harvest in as little as 2 ½ to 3 months from when you put the seeds in the ground.
The downside is that, typically, they are less potent, but autoflower seeds are great for people who want to grow cannabis but don’t want to spend a lot of time doing it.