Javascript Date calculateMonths(fromDate, toDate)

function calculateMonths(fromDate, toDate) {
  var fromDateObject = new Date(fromDate),
  toDateObject = new Date(toDate),
  timeDifference = toDateObject.getTime() - fromDateObject.getTime(),
  millisecondsPerMonth = 1000*60*60*24*30;

  return Math.round(timeDifference/millisecondsPerMonth);
}