I dont think a little less than 12hrs of light can hurt anything besides MAYBE final production. There are plenty of places where marijuana would grow in the wild that would get less than 12 hours of light at some. I use to grow in washington. by end of september and and start of october the sun came up at 7 and was down at 6. that was about half way thru flower cycle they started getting 13/11 naturally. 12/12 is just most common!