In as little as 3 weeks a seed can be mature after successful pollination. What determines the actual speed i'm not exactly sure. Everyone says to give 30 days or more for seeds to mature before harvesting a plant that was pollinated, and that's good advice for a layman gardener or the average home medicinal grower, but the actual true answer to
how many days a seed needs to reach maturity
as little as 21 days. ive witnessed even faster speeds of a seed maturing, but 3 weeks is the safest statement. When everyone regurgitates "4-6 weeks for seeds to mature", that's one of those things the pros don't care if that bro science myth gets perpetuated cuz it aint hurting anyone. if anything it helps keep the drama and fighting down, but let it be known, if everything is right, seeds dont need that long....the plant may need a whole month to mature all the seeds, but an individual seed in an ideal situation is done super fast.
Did you know you can cut a branch from a flowering plant, put it in vase of water and mild nutes, pollinate it, and it will finish those seeds, even in 24/7 light schedule.