Javascript time between two days

<!DOCTYPE html>
<html lang="en">
  <head>
    <title>Until Vacation TIME!!!</title>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-alpha.6/css/bootstrap.min.css" crossorigin="anonymous">
    <!--https://github.com/datejs/Datejs-->
    <script src="https://cdnjs.cloudflare.com/ajax/libs/datejs/1.0/date.min.js"></script>
    <script src="https://code.jquery.com/jquery-3.1.1.slim.min.js" crossorigin="anonymous"></script>
    <script src="https://cdnjs.cloudflare.com/ajax/libs/tether/1.4.0/js/tether.min.js" crossorigin="anonymous"></script>
    <script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-alpha.6/js/bootstrap.min.js" crossorigin="anonymous"></script>
    <script>
      var today = new Date().toString('M/d/yyyy');
      var day = "11/16/2017";
      $(document).ready(function(){
        //get time between dates;
        var b = dateDiff(today,day,"d");
        $("#main").html("There are " + b + " days until " + day);
      });

      function toDate(s) {
        var s = s.split('/');
        return new Date(s[2], --s[0], s[1]);
      }

      function dateDiff(from,to,format) {
        var milliseconds = toDate(to) - toDate(from);
        var days = milliseconds / 86400000;
        var hours = milliseconds / 3600000;
        var weeks = milliseconds / 604800000;
        var months = milliseconds / 2628000000;
        var years = milliseconds / 31557600000;
        if (format == "h") {
          return Math.round(hours);
        }
        if (format == "d") {
          return Math.round(days);
        }
        if (format == "w") {
          return Math.round(weeks);
        }
        if (format == "m") {
          return Math.round(months);
        }
        if (format == "y") {
          return Math.round(years);
        }
      }
    </script>
  </head>
  <body>

    <div id="main" class="container">

    </div>

  </body>
</html>