outdoor flowering question

I want to start flowering my outdoor crop becasue they are suffering alot of abuse. I have about 20 plants in pots. I want to hang a tarp or make a tent or something. Do they need to be completely in darkness for 12 hrs or is a completly shaded area with no sun enough darkness?
also any ideas on my tent/tarp structure?

Rays still come down in shade or not...the best way for outdoors is to get it as close to 12 hours of sun and 12 hours dark as possible..You could get an ice fishing shante that are completely black and just use that instead of building a tent...Just my two cents

Easily, Black garbage bags