function set_date(el){ 
  if(el.style.backgroundColor == '' || el.style.backgroundColor == 'white'){
    el.style.backgroundColor = '#BBBBBB';
    el.style.color = 'white';
    new_el = document.getElementById('log').value;
    document.getElementById('log').value = new_el + 'add' + el.id + ';';
  }
  else if(el.style.backgroundColor == 'rgb(187, 187, 187)'){
    el.style.backgroundColor = '';
    el.style.color = '#505050';
    new_el = document.getElementById('log').value;
    document.getElementById('log').value = new_el + 'del' + el.id + ';';
  }
  return;
}

function set_year(enable, disable){
  document.getElementById('rok_'+enable).style.display = 'block';
  document.getElementById('rok_'+disable).style.display = 'none';
  return;  
}