Light schedule questions

I have my plants on 12/12 ( plants in flowering ) but i was thinking about changing the time the lights come on. at the moment i have them off in the day and on in the night but i wanted to change it to the other way around.
All i want to know is what would be the best thing to do without affecting my plants -
1. Leave the lights off for the extended period, or
2. leave the lights on for the extended period of time...

I've done both with no bad results. I think most people believe it is the dark period that matters so that would be to leave them off for the extended period. Unless your plants are prone to hermaphroditism, then I wouldn't worry too much. Some other people may have good insight too.

cheers pal