function countdown()
{
starttime=starttime+1;
begintime=ende - starttime;

if (begintime <=0){begintime=0;}

var eintag=86400;
var einestunde=3600;
var eineminute=60;

var tage = begintime / eintag;
tage = Math.floor(tage);

if (tage == 1)
{
var zeigetage="TAG";
}
else
{
var zeigetage="TAGE";
}

var rest= begintime - (tage * eintag);

var stunde= rest / einestunde
stunde = Math.floor(stunde);

if (stunde < 10)
{
stunde="0"+stunde;
}

var rest = rest - (stunde * einestunde);

var minute = rest / eineminute;
minute=Math.floor(minute);

if (minute < 10)
{
minute="0"+minute;
}

var rest = rest - (minute * eineminute);

if (rest < 10)
{
rest="0"+rest;
}

document.getElementById('countdown').innerHTML= tage+" "+zeigetage+" - " + stunde + ":" + minute + ":" + rest;
}

function gocountdown() {
  setInterval( "countdown()", 1000 );
  return true;
}