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;
}