Unless you're planning on working with a non-standard day period (i.e. 12 hours of darkness and 18 hours of light) this sounds like a riddle!
Let's use the Gas Lantern Routine as an example. That would be 12/5.5/1/5.5 where the 12 and the 1 are light and the 5.5 are dark. A plant under GLR lighting will not go into flower as it doesn't get 12 hours of darkness. However, neither do outdoor plants and they go into flower merely because they begin getting less light than they did the day before. Or is it because they get more dark? How would you test that except by using a non-24 hour day.
Archiweedies' Durban Poison went into flower because he went from 18/6 to 16/8, as an outdoor grow would.
So I don't know the answer - if there is one! Sorry
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