var x = new Date().getHours();

if (x >= 18 || x <= 5) {
 
    document.getElementById('topTitle').setAttribute("src", "../img/titlen.jpg");
    document.getElementById('imgHD').setAttribute("src", "../img/kcn.jpg");
    //var dd = document.getElementById('imgHD');
    //dd.setAttribute("src", "../img/kcn.jpg");

}