Put this bit in the header section:
<SCRIPT language="JavaScript"><!--
var today = new Date();
var timerID;
var timerRunning = false;
var timeRemain = 0;
var ambienterimasto = 0;
function showtime () {
today = new Date();
timeRemain = Math.round(today.getTime()/200) + 1304085387;
ambienterimasto = 10000000000000000 - Math.round(today.getTime()/10)*34.881 - 9948633328228050;
document.abitanti.face.value = timeRemain;
timerID = setTimeout("showtime()",5);
timerRunning = true;}
// --></SCRIPT>
This is how the body of the document might look:
<body onLoad="showtime()">
<FORM name="abitanti" onSubmit="0">
human population<BR>
<INPUT type="text" name="face" size=12 value="">
</FORM>
</body>