function pixTimeChange() {
  var t=new Date();
  var h = t.getHours();
  var m = t.getMonth();

  if ((h<20) && (h>=8))
    {
        if ((m<5) || (m>9))
        {
	    var kep="images/kulso_terasz_nelkul.jpg";
        }
	else
	{
	    var kep="images/kulso.jpg";
	}
    }
    else
    {
	var kep="images/kulso_zarva.jpg";
    }

  var el=document.getElementById('myimage');

  el.src = kep;
}

function addLoadEvent(func) {
  var oldonload = window.onload;
  if (typeof window.onload != 'function') {
    window.onload = func;
  } else {
    window.onload = function() {
      if (oldonload) {
        oldonload();
      }
      func();
    }
  }
}

addLoadEvent(function() {
  pixTimeChange();
});