Seems to me......
The best time to go fluking is when you're in NC....
Inlets/rivers/sound.....13" "NO Limit" (not that I agree with this)
Ocean......15.5" Eight per day
Lot of work to go Flounder fishing around here, plus the $$$, and rarely come home with fish for the table. Seems we could do something to the effect of 2 fish at 16, and the rest be 17.5. I don't know, but it sure is frustrating going from the old 15" size limit, to 17.5. Enough that since it was my primary fishing, just sold my boat after the limits went up. Could'nt rationalize the cost to the catch anymore. Just have to target other species for the most part now.
To answer your question, IMO Daytime for sure, although I won't say I "never" caught one at nite, but night time is more condusive to gigging.