var counterObject;

if (counterObject = document.getElementById("countdown")) {
   var finalDate = counterObject.innerHTML;

   var end = new Date(finalDate);
   var endOffset = end.getTime() / 100;

   calcTime();
   setInterval("calcTime()", 100);
}

function calcTime() {
   var now = new Date();
   var startOffset = now.getTime() / 100;

   var length = Math.floor(endOffset - startOffset);

   days = Math.floor(length / 864000);
   length = length % 864000;

   hours = Math.floor(length / 36000);
   length = length % 36000;

   minutes = Math.floor(length / 600);
   length = length % 600;

   seconds = length / 10;

   // Add trailing zero for seconds, i.e. 5 becomes 5.0
   if (length % 10 == 0) seconds += ".0";

   // If the deadline has been passed, set everything to zero
   if (endOffset < startOffset) {
      days = hours = minutes = seconds = 0;
   }

   var finalString = days + " days, " + hours + " hours, " + minutes + " minutes, " + seconds;

   document.getElementById("countdown").innerHTML = finalString;
}