function countdown() {
   var now = new Date();
   var end = new Date(2013,11,31,0,0,0);
   var countdown = parseInt((end.getTime() - now.getTime()) / (1000 * 60 * 60 * 24));
   document.getElementById("countdown").replaceChild(document.createTextNode(countdown + " Tage"), document.getElementById("countdown").firstChild)
}