They're not going to believe you, Wet. Photoperiodism is a myth, obviously.
Back to reality. I just love how persons with no comprehensive or formal knowledge of botany or biology feel so confident in themselves and their personal experiences that they go on internet forums touting things as myth because of things like little red LED lights in a grow room. Some of this is understandable because we see things and we're like "hey... I see that", yet we fail to realize that the very way in which we see is fundamentally biased due to the way our eyes evolved. Here we assume that because we see some light, and because these plants are supposedly photosensitive; well why don't we see any effect? Or maybe we do see an effect but we've already made up our minds that this whole thing is a myth so it must be due something else...
Where I am going with this is that the manner in which we see/perceive light, with our iris, pupils, lens, ciliary muscles, retina (with its rods and cones), macula, optic nerve, etc... is so intrinsically and enormously different than how plants detect it (proteins: phytochrome, cryptochrome) that it seems quite outrageous to me that someone could see light from the moon or a little red LED bulb and come to the conclusion that light during the dark period having any effect on plants must be a myth. That's just baffling because first of all plants and humans don't even share the exact same 'visible spectrum'; and then we have the fact that our eyes physically change with lighting. Our eyes are a bit complex, and actually adapt to changes in lighting (photopic to scotopic). First our pupils can dilate and constrict to control the amount of light that reaches the retina. Then over time our rods and cones can actually adjust; color perception changes (particularly how we perceive black) and our eyes can become hundreds of thousands of times more sensitive to light.
So to exclaim that light leaks causing stress/hindering flowering is a myth because you 'see' the moonlight is ridiculous once you understand a little bit about how a human eye works. Then we can go on to consider that the moon's light is actually reflected from the sun, and how the intensity of the moonlight fluctuates dependent on phase, and how even a full moon is 500,000 times fainter than a sunny day.
The fact remains that Cannabis sativa and indica are 'short-day' plants. They need near total darkness to flower, like other short-day plants. A sufficient amount of light for a sufficient duration of time could interrupt the flowering of a short-day plant; any short-day plant, not just cannabis. Notice how I am not exclaiming that the tiniest light leak in your grow room is going to turn a plant into a hermaphrodite. Some plants might be more sensitive than others. Feminized plants in particular I would stay away from regardless because of their tendency to turn... and for them especially it would be a good idea to let your dark period be as dark as possible.
Now, if you plan on breeding anything then by all means shine copious amount of light on your plants during the dark period to expose the ones that are easily stressed... but if you're just growing out plants for buds you probably don't want them to go hermie if you can help it.
