XML : Error date NaN in firefox and IE

Hello I need to spend a given XML through javascript to subtract the current date and time date.

What makes this code is to show the remaining time of a song streaming in minutes and seconds

And then with javascript parsing date and I transform in milliseconds and the current date will also rest in ms.

In Chrome date shows me perfectly, but in Mozilla and IE NaN console shows me and gives error. I do not understand is that if I have parsed the date because it only works in Chrome. There must be a mistake.

PHP (I draw the start date of a song)

     <?php    $xml = @ simplexml_load_file('http://www.example.com');  foreach ($xml as $track){    $startTime = $track->starttime;   $songDuration = $track->playduration;    }  ?>    

JAVASCRIPT: var spend javascript

      var tiempoComienzo= "<?php echo $startTime ?>";        var cancionDuracion="<?php echo $songDuration ?>";          //parse delivered date from php        var d = new Date(Date.parse(tiempoComienzo));        //PHP get the date in milliseconds        var resultPHPms = d.getTime();        //get the current date        var f = new Date();        //step the current date to milliseconds        var resultJSms = f.getTime();        //adding the date of the song to the length of the song        var inicioMasCancion=parseInt(cancionDuracion) + parseInt(resultPHPms);         //It is the challenge to the current date        var TiempoRestante=inicioMasCancion-parseInt(resultJSms);        //pass the result to seconds        seconds=(TiempoRestante/1000)          var container = document.getElementById('time');      var seconds = parseInt(seconds+7);    //step seconds to minutes and seconds            var minutes = parseInt( seconds / 60 ) % 60;      var seconds = seconds % 60;          var contadorDeTiempo=(minutes < 10 ? "0" + minutes : minutes) + ":" + (seconds  < 10 ? "0" + seconds : seconds);            countdown(seconds);    

function countdown:

  <script>    var timer;  function countdown(seconds) {  seconds--;        if(seconds >= -1) {      container.innerHTML =contadorDeTiempo;  }  }  timer = setInterval(countdown, 1000);      </script>    

HTML:

  <span id='time'></span>    

In chrome it is perfectly displayed and works perfect. But in Mozilla and IE console NaN it is shown, specifically in this line:

  var d = new Date(Date.parse(tiempoComienzo));    

How I could solve? The resulting XML date is as follows:

  2015-12-20 12:45:33.17    

thanks very much for your help