window.onload=startTime();

function startTime()
{
	var today=new Date();
	var h=today.getHours();
	checkBG(h);
		}

function checkBG(i)
{
	if (i>0 && i<=18) {
		setActiveStyleSheet('default');
	} else {
		setActiveStyleSheet('alternate');

	}
}


function setActiveStyleSheet(title) {
  var i, a, main;
  for(i=0; (a = document.getElementsByTagName("link")[i]); i++) {
    if(a.getAttribute("rel").indexOf("style") != -1 && a.getAttribute("rel").indexOf("alt") != -1) {
      a.disabled = true;
    if(a.getAttribute("rel").indexOf(title) != -1) a.disabled = false;
    }
  }
}