javascript calculate days between dates
function calculateDaysBetweenDates(date1, date2) {
var oneDay = 24 * 60 * 60 * 1000;
var date1InMillis = date1.getTime();
var date2InMillis = date2.getTime();
var days = Math.round(Math.abs(date2InMillis - date1InMillis) / oneDay);
return days;
}