When will I start seeing signs of gender?

Hard to say since you started flower early, but could be any day now, keep a'watchin...

 

yeah, I'm with Toasty. You started a bit early, so things will be off the normal schedule - whatever "normal" is.

You will typically see male flowers 1-2 weeks in and female flowers 1.5 or 2 weeks to 3 weeks. Depends on the strain and growing conditions. You mileage may vary.

 

16 days of 12/12 and no signs of sex yet? Is the plants dark period 100% pitch black dark? Maybe it is a strain thing or you prunned right before going to 12/12 or something. Make sure they are totally dark at night.

 

Often you cannot force flower a plant. Most MJ plants MUST preflower before you can flower them out. If you are 12/12ing your plant before it preflowers you are just slowing down how long it will take to preflower. Put your lights back up to 18/6 untill your plants show their sex. That is why cloning is so good, because you can take the already preflowered cuttings and place them right into 12/12. My experience has shown me this is strain dependant. Indicas will show quicker than sativas. But my guess would be it takes normally about 1 to 1 1/2 months.