var LastClockMin = 0;
var LastClockStd = 0;

function updateClock() {
 var jetzt = new Date();
 var Std = jetzt.getHours();
 var Min = jetzt.getMinutes();
 if (LastClockMin == Min && LastClockStd == Std)
    return;
 LastClockMin = Min;
 LastClockStd = Std;    

 for( var i = 0; 6 > i; ++i) {
   e = document.getElementById("m" + i);
   b = Min % 2;
   Min = (Min - b) / 2;
   if (b == 0) e.className = "off"
   else e.className = "on"; 
 }

 for( var i = 0; 5 > i; ++i) {
   e = document.getElementById("h" + i);
   b = Std % 2;
   Std = (Std - b) / 2;
   if (b == 0) e.className = "off"
   else e.className = "on"; 
 }

} 

updateClock();

window.setInterval("updateClock()", 490);