I've studied that chart before a coupla months ago, and it says that 12/12 where I live is September 26...a month and a half away. After further studying and research, I've learned that outdoor grown marijuana tends to begin flowering earlier than 12/12, or rather 15/9 or 14/10, 13/11.
This should be the case here with mine, since I just noticed REAL signs of flowering on my 4 month old today, which according to the chart makes it 14.5/9.5 today.
Hope this helps! GL everyone!