var daysToAdd = -30;
var temp_date = new Date(dispDate);
temp_date = new Date(temp_date.getTime() + daysToAdd*24*60*60*1000);
var rtnMonth = temp_date.getMonth() + 1;
var rtnDay = temp_date.getDate();
var rtnYear = temp_date.getYear();
alert(rtnMonth+"/"+rtnDay+"/"+rtnYear);
