Hey you want to give it a 48 hour dark period when it is time and ready to harvest. The only reliable way to know when to harvest is to monitor your trichomes with a 30x or better 60x magnifying glass. You want to harvest with the highest percentage of cloudy milky trichomes as possible. Clear trichs=not ready. cloudy=reaching maximum thc level. amber= too late your thc is converting to cbd and other less desirable compounds. I start flushing when I get about 10% amber and they are usually good for me in about a week. You will get different effects depending on when you harvest. A early harvest with several clear trichs will give you more of an energetic high where a late harvest with a lot of amber will give you more of a sedative couchlock effect. It is really something you have to experiment with to see what you like. When about 50% of your hairs are brown it is a good time to start monitoring the trichomes.