How is this done?

<HTML>
<HEAD>

<SCRIPT>

<!-- Countdown Script by Virtual_Max             -->
<!-- http://come.to.vmax                         -->
<!-- please keep this comment unchanged if you use it  -->

<!-- hide script
//change your event date event here.
var eventdate = new Date("January 1, 2005 00:00:00 GMT");

 function toSt(n)
 {s=""
  if(n<10) s+="0"
  return s+n.toString();
 }
 
 function countdown()
 {cl=document.clock;
  d=new Date();
  count=Math.floor((eventdate.getTime()-d.getTime())/1000);
  if(count<=0)
    {cl.days.value ="----";
     cl.hours.value="--";
     cl.mins.value="--";
     cl.secs.value="--";
     return;
    }
  cl.secs.value=toSt(count%60);
  count=Math.floor(count/60);
  cl.mins.value=toSt(count%60);
  count=Math.floor(count/60);
  cl.hours.value=toSt(count%24);
  count=Math.floor(count/24);
  cl.days.value=count;    
  
  setTimeout("countdown()",500);
 }
// end script -->

</SCRIPT>
</HEAD>
<BODY TEXT="#FFFF80" BGCOLOR="#000000" LINK="#80FF00" VLINK="#FF00FF" ALINK="#FF0000" 
 onLoad="countdown()">

<center>
<P>

<FORM name="clock"></P>
<CENTER>

<TABLE BORDER=5 CELLSPACING=5 CELLPADDING=0 BGCOLOR="#000000" >
<TR>
<TD ALIGN=CENTER WIDTH="31%" BGCOLOR="#000080"><B>Days:</B></TD>
<TD ALIGN=CENTER WIDTH="23%" BGCOLOR="#000080"><B>Hours:</B></TD>
<TD ALIGN=CENTER WIDTH="23%" BGCOLOR="#000080"><B>Mins:</B></TD>
<TD ALIGN=CENTER WIDTH="23%" BGCOLOR="#000080"><B>Secs:</B></TD>
</TR>

<TR>
<TD ALIGN=CENTER><INPUT name="days" size=4></TD>
<TD ALIGN=CENTER><INPUT name="hours" size=2></TD>
<TD ALIGN=CENTER><INPUT name="mins" size=2></TD>
<TD ALIGN=CENTER><INPUT name="secs" size=2></TD>
</TR>

<TR>
<TD COLSPAN="4" BGCOLOR="#000080">
<center><FONT SIZE=+2>Left before:</FONT></center>
</TD>
</TR>

<TR><TD COLSPAN="4" BGCOLOR="#000000"><CENTER><FONT SIZE=+1 COLOR="#00FF00">
<script>
 document.write(" "+eventdate.toGMTString()+" ");
</script>
</FONT></CENTER></TD></TR>

</TABLE></CENTER>

<P></FORM></P>

</BODY>
</HTML>