function CountDown(live) {
	    var time = new Date();
	    var diff = live - time;
		return diff;
	}

	var liveDate = "April 28, 2016 14:19:00 PDT";

	if (CountDown(new Date(liveDate))>0) { //pre-live
		ad_img.src="https://s.yimg.com/cv/ae/us/audience/160429/640x100xtiqj3go3.jpg";
	} else {//live now
		ad_img.src="https://s.yimg.com/cv/ae/us/audience/160429/640x100xtiqj3fzh.jpg";
	}