var xmlHttp;

function createXMLHttpRequest() {
  if (window.ActiveXObject) {
    xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
  }
  else if (window.XMLHttpRequest) {
    xmlHttp = new XMLHttpRequest();
  }
}

function startQuery(date) {
  var url = "http://www.zemplin.org/calendar.php?calendar="+date;
  createXMLHttpRequest();
  xmlHttp.onreadystatechange = handleStateChange;
  xmlHttp.open("GET", url, true);
  xmlHttp.send(null);
}

function handleStateChange() {
  if(xmlHttp.readyState == 4) {
    if(xmlHttp.status == 200) {
      document.getElementById("calendar").innerHTML = xmlHttp.responseText;
    }
  }
}