var hlaska = "Čas už uplynul";

function odpocet(prvek, cil)
  {
    var el = document.getElementById(prvek);

    if(!el) return;

    var casovac = setInterval(aktualizace, 1000);

    function aktualizace()
      {
        var ted = new Date().getTime();
        var diff = cil - ted;

        if(diff <= 0)
          {
            el.innerHTML = hlaska; clearInterval(casovac);
            return;
          }

        var tmp = diff / 1000;
        var d = Math.floor(tmp / 86400);

        tmp = tmp % 86400;

        var h = Math.floor(tmp / 3600);

        tmp = tmp % 3600;

        var m = Math.floor(tmp / 60);

        tmp = tmp % 60;

        var s = Math.floor(tmp);
        var casStr = "";

        if(d > 4) casStr = d + " dní,   ";
        else if(d > 1) casStr = d + " dny,   ";
        else if(d > 0) casStr = d + " den,   ";

        if(h < 10) casStr += "0";
        casStr = casStr + h + ":";

        if(m < 10) casStr += "0";
        casStr = casStr + m + ":";

        if(s < 10) casStr += "0";
        casStr = casStr + "" + s;

        el.innerHTML = casStr;
      }
  }
window.onload = function(){
  odpocet("zamosti", Date.UTC(2010, 5, 4, 15, 0)); // (rok, mesic-1, den, hodina-1, minuta) 4.6.2010 16:00 UTC, 4. cervna 16:00
  //odpocet("predprodej", Date.UTC(2010, 3, 30, 22, 59)); // (rok, mesic-1, den, hodina-1, minuta) 30.4.2010 23:59 UTC, 30. dubna 23:59
  odpocet("predprodej", Date.UTC(2010, 5, 3, 22, 59)); // (rok, mesic-1, den, hodina-1, minuta) 3.6.2010 23:59 UTC, 30. dubna 23:59
}