sunlight/box

I have five strains ,four from seed, and one from a clone. I am in South Africa so they are almost a meter tall and should flower naturally soon. However, I want them to flower (apart from the clone mother.) quickly so that I can sex them. So I have started leaving them in the bright sunshine for twelve hours, and then into a totally dark vented box for twelve hours. Is this gonna work? THANKS.
 
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