Ember Cli - Added Polyfill Internet Explorer Error Object Expected

I have a problem and I don't see someone who has this kind of problem with this. Basically I made a helper to format a date, it has some syntax of EcmaScript like let, or expoorts. Its working in all the browsers except INTERNET EXPLORER, so I though ok its time to configure Polyfill, so I read the documentation to configure it with ember-cli-babel and I am not able to see the results as expected.

I have an ember app, with ember cli

DEBUG: -------------------------------
DEBUG: Ember  : 2.14.1
DEBUG: jQuery : 2.2.4
DEBUG: -------------------------------

I include POLYFILL in my broccoli file like this ember-cli

var EmberApp = require('ember-cli/lib/broccoli/ember-app');

module.exports = function(defaults) {
  var app = new EmberApp(defaults, {
    'ember-cli-babel': {
      includePolyfill: true
    },
    storeConfigInMeta: false,
    minifyJS: {
      enabled: false
    },
    minifyCSS: {
      enabled: false
    },
    vendorFiles: {
      'jquery.js': {
        development: 'bower_components/jquery/dist/jquery.js',
        production: false,
        development: false
      }
    }
  });

  app.import('vendor/jquery.lumanetix.all.min.js');

  return app.toTree();
};

I have a ember helper to format a date here it is:

import Ember from 'ember';

export function dateAuctionFormat(date/*, hash*/) {
  let dateObj = new Date(date);
  let monthName = getMonthName(dateObj.getUTCMonth());
  let dayNumber = dateObj.getUTCDate();
  dayNumber = dayNumber + formatDateNotation(dayNumber);
  let dayName = getWeekDayName(dateObj.getDay());
  let time = dateObj.toLocaleString('en-US', { hour: 'numeric', minute:'numeric', hour12: true });
  return dayName + ' ' + dayNumber + ' ' + monthName +  ' ' + time;
}

function getMonthName(date) {
  let month = [];
  month[0] = "Jan";
  month[1] = "Feb";
  month[2] = "March";
  month[3] = "April";
  month[4] = "May";
  month[5] = "June";
  month[6] = "July";
  month[7] = "Aug";
  month[8] = "Sept";
  month[9] = "Oct";
  month[10] = "Nov";
  month[11] = "Dec";
  return month[date];
}

function getWeekDayName(date) {
  let weekday = new Array(7);
  weekday[0] =  "Sunday";
  weekday[1] = "Monday";
  weekday[2] = "Tuesday";
  weekday[3] = "Wednesday";
  weekday[4] = "Thursday";
  weekday[5] = "Friday";
  weekday[6] = "Saturday";
  return weekday[date];
}

function formatDateNotation(d) {
  if (d > 3 && d < 21) {
    return 'th';
  }

  switch (d % 10) {
        case 1:  return "st";
        case 2:  return "nd";
        case 3:  return "rd";
        default: return "th";
    }
}

export default Ember.Helper.helper(dateAuctionFormat);

But when Internet Explorer 11 is rendering the site, I have an error in the debugger like this:

The error said Object Expected. and you can see the error showing just after the line

export default App.extend({
  // rootElement: '#listings-search'
});

So I don't know from where start, I try to modify a little bit, app.js, but no luck, also I tried to convert my ES6 code to ES5 with this converter: http://ift.tt/1AQUemp

But of course it didn't work and also its not the idea.