Is that okay to arrive on 179 day ?how uscis count days of your presence in usa?does partial day spent in usa is considered full

I am permanent resident here since DEC 2011.I have plans to visit on 14 Aug 2016 to 9 Feb 2017. after booking my tickets I noticed that my trip is 179 days long.like when I arrive in 9th Feb it will be 179th day is