So basically in order to get the exact day you wanna harvest your going to need some tools . Either a portable microscope or some micro lenses for your smart phone . You can get a micro lense from places such as wal mart , amazon , camera stores and for the portable microscope you can go to amazon or your local garden shop for that they are common . Now moving on to the actual question. It's a matter of preference . But to get top shelf stuff I usually go 1 or 2 weeks past the breeders recommendations sometimes longer . The plant will tell you when shes near ready . Leaves will start turning yellow for seemingly nothing , buds will stop swelling , no new pistols will form up there are lots of signs that you're close . But without certain tools it's hard to give a precise day . I hope this info serves you well on your journey ! Happy Growing!