var req;

function navigate(month,year) {
	var url = "inc/calendar.php?month="+month+"&year="+year;
	if(window.XMLHttpRequest) {
		req = new XMLHttpRequest();
	} else if(window.ActiveXObject) {
		req = new ActiveXObject("Microsoft.XMLHTTP");
	}
	req.open("GET", url, true);
	req.onreadystatechange = callback;
	req.send(null);
}

function callback() {
	if(req.readyState == 4) {
		if(req.status == 200) {
			response = req.responseText;
			document.getElementById("calendar").innerHTML = response;
		} else {
			alert("There was a problem retrieving the data:\n" + req.statusText);
		}
	}
}