function startTimer() {
  var serverTime = getTime(document.getElementById("serverTime"));
  timeDiff = serverTime-1
  timeStart = serverTime;

  // Nach span mit der Klasse timer und timer_replace suchen
  var spans = document.getElementsByTagName("span");
  for(var span_id in spans) {
    var span = spans[span_id];
    if(span.className == "timer" || span.className == "timer_replace") {
      startTime = getTime(span);
      if(startTime != -1)
        addTimer(span, serverTime+startTime, (span.className == "timer"));
    }
  }