var date = new Date();
    var hours = date.getHours();
    if ( (hours < 6) || (hours >= 19) ) {
        // document.write('<style>body { background-color: #ff0000; }</style>');
    } else {
        // document.write('<style>body { background-color: #ff0000; }</style>');
        document.backgroundcolor = '#ff0000';
    }