yeah man when i was growing back in the day and my parents would come into town i would just shut it down, even when the plants were flowering and close the opperation for the weekend. its not like you can control the pwer going off. start a fresh 12/12 cycle when the power comes back, and you should be fine. as long as your power hasnt been off for a few days. (the plant doesnt have a clock inside, were it has to have exactly 12/12). on my grow now my timer doesnt even have 12/12 but i get it close and it works. so dont worry man.