Displaying countdown time on webpage

Some times we need to diaplay countdown time on the webpage. Here is a small javascript code to display countdown time on the webpage.

 Countdown time





          [clock2]





countdown_start("timer","07/29/2009 2:00 PM")  

   function countdown_start(divid,givendate)

  {

          var given_date          = new Date(givendate);

          var cur_date          = new Date();

          diff = new Date(given_date - cur_date);

          secs = Math.floor(diff.valueOf()/1000);

              count_back(divid,secs);

  }

 

  function calculate(secs, num1, num2)

  {

           s = ((Math.floor(secs/num1))%num2).toString();

          if (s.length < 2)

          {       

                    s = "0" + s;

          }

              return (s);

  }

 

  function count_back(divid,secs)

  {

          var output;

          var format = "%%D%% Days %%H%%:%%M%%:%%S%%";

          output = format.replace(/%%D%%/g,calculate(secs,86400,100000));

          output = output.replace(/%%H%%/g,calculate(secs,3600,24));

          output = output.replace(/%%M%%/g,calculate(secs,60,60));

          output = output.replace(/%%S%%/g,calculate(secs,1,60));

          if(secs > 0)

          {       

                    document.getElementById(divid).innerHTML = output;

                    setTimeout("count_back('" + divid + "'," + (secs-1) + ");", 990);

          }

          else

          {

                    document.getElementById(divid).innerHTML = "Auction Over";

          }

  }