function checkTime(){
	
	var d = new Date();
	var h = d.getHours();
	
	if(h < 6 || h >= 18){
		switch_style('night');
	}else{
		switch_style('day');
	}
	
}

function switch_style ( css_title )
{
	var link_tag,i;
	
	link_tag = document.getElementsByTagName("link");
	
	for (i = 0; i < link_tag.length ; i++ ) {
		
		//if link is a stylesheet and has a title
    	if ( (link_tag[i].rel.indexOf( "stylesheet" ) != -1) && link_tag[i].title) {
			
			link_tag[i].disabled = true;//disable all stylesheets
      		
			//if matches the passed in sheet, enable style sheet
			if (link_tag[i].title == css_title || link_tag[i].title == "default") {
        		link_tag[i].disabled = false;
      		}
    	}
  	}
}