now = new Date(); // create new Date object
hour = now.getHours(); // from that date, grab current hour
if (hour >= 0 && hour < 5 ) {document.write("Goedenacht!");}
if (hour >= 5 && hour < 12) {document.write("Goedemorgen!");}
if (hour >= 12 && hour < 18) {document.write("Goedemiddag!");}
if (hour >= 18 && hour < 24) {document.write("Goedenavond!");}