Do sekce body umφst∞te:
<script>
function tick() {
var hours, minutes, seconds, ap;
var intHours, intMinutes, intSeconds;
var today;

today = new Date();

intHours = today.getHours();
intMinutes = today.getMinutes();
intSeconds = today.getSeconds();

if (intHours == 0) {
hours = "12:";
ap = "Midnight";
} else if (intHours < 12) {
hours = intHours+":";
ap = "dopoledne";
} else if (intHours == 12) {
hours = "12:";
ap = "Poledne";
} else {
intHours = intHours - 12
hours = intHours + ":";
ap = "Odpoledne";
}

if (intMinutes < 10) {
minutes = "0"+intMinutes+":";
} else {
minutes = intMinutes+":";
}

if (intSeconds < 10) {
seconds = "0"+intSeconds+" ";
} else {
seconds = intSeconds+" ";
}

timeString = hours+minutes+seconds+ap;

Clock.innerHTML = timeString;

window.setTimeout("tick();", 100);
}

window.onload = tick;

</script>