It only took 4 hour power outage for my clones. They were clones and I had already revegged them when I took them as clones. I hope that is why and not just the lights being off. We will see. These ***** I live with know not to touch my plants. They always kill or manage to ruin them somehow.I had that happen a few times, and they didn't start flowering. I think it takes more than a single day.