function hodiny()  {
  today   = new Date();
  hours   = today.getHours();
  minutes = today.getMinutes();
  seconds = today.getSeconds();
  timeValue = hours;
  timeValue += ((minutes < 10) ? ":0" : ":") + minutes;
  timeValue += ((seconds < 10) ? ":0" : ":") + seconds;
  document.getElementById("cas").innerHTML =  timeValue;
  window.setTimeout("hodiny()",1000);
}