function updateClock (id, deadline)
{
  var currentTime = new Date ( );
  var interval = deadline - Math.round(currentTime.valueOf() / 1000);
  if (interval<0) {
    interval = -interval;
    var sign = '-';
  }
  else sign = '';
  
  var secs = interval % 60;
  interval = Math.floor(interval / 60);
  var mins = interval % 60;
  interval = Math.floor(interval / 60);
  var hrs = interval % 24;
  var days = Math.floor(interval / 24);

  if (secs<10) secs = '0' + secs;
  if (mins<10) mins = '0' + mins;
  days = days?days+(days>1?' dni ':' dzień '):'';
  var currentTimeString = sign+days + hrs + ":" + mins + ":" + secs;

  document.getElementById(id).innerHTML = currentTimeString;
}