function hora(id) {
  var tid = new Date();
  var div = document.getElementById(id);

  var h = tid.getHours();
  var ap = " p.m.";
  if ( h > 12 ) {
  h = h-12;
  } else { ap = " a.m."; };
  hrs = (h>=10)?(""+h):("0"+h);
  m = tid.getMinutes();
  mns = (m>=10)?(":"+m):(":0"+m);
  s = tid.getSeconds();
  scs = (s>=10)?(":"+s):(":0"+s);
  div.innerHTML = hrs+mns+scs+ap;

  window.setTimeout("hora('"+id+"');",999);
}