question about flowering photoperiod

it is my understanding that for a plant in the flowering stage, there must be no light at all for more then twelve hours. when my plants get to the flowering stage, i'm transplanting them to the space behind my (wooden) back fence, so that they will be in shade for most of the day. they'll have about three or so hours of twilight when the sun is still up, but the light is blocked by the fence.

my question is, if there is still a tiny bit of indirect sunlight for a part of the "night", will this affect how the plant flowers?

 

They need to be in the DARK...not the aurora borealis....

Seriously, dark has to be dark...night~!

 

The rule is: No light brighter than that of the full moon.

Multiple light interruptions = hermies (even the 5th dentist agrees).