function calendar(id,fieldid,monthadd)
{
  var now=new Date();
  
  monthadd=monthadd||0;
  var month=now.getMonth()+monthadd;
  var yearadd=0;
  while(month>=12)
  {
    month-=12;
    yearadd++;
  }
  while(month<0)
  {
    month+=12;
    yearadd--;
  }
  var year=now.getFullYear()+yearadd;
  
  
  var daysinmonth=32 - new Date(year-1900,month, 32).getDate();
  date=new Date(year-1900,month,1);
  var dayinweek=date.getDay();
  var monthnames=Array("Leden","Únor","Březen","Duben","Květen","Červen","Červenec","Srpen","Září","Říjen","Listopad","Prosinec");
  //alert(dayinweek);
  var numrows=Math.ceil((daysinmonth+dayinweek)/7);
  var i,j,day;
  var string="<table class='kalendar'><tr class='kalendarhead'><td onclick='calendar(\""+id+"\",\""+fieldid+"\","+(monthadd-1)+")'>&lt;</td><td colspan='5' style='text-align:center'>"+monthnames[month]+"</td><td onclick='calendar(\""+id+"\",\""+fieldid+"\","+(monthadd+1)+")'>&gt;</td></tr><tr class='kalendardays'><td>Po</td><td>Út</td><td>St</td><td>Čt</td><td>Pá</td><td>So</td><td>Ne</td></tr>";
  var day=0;
  if(dayinweek==6) day=1;
  for(i=0;i<numrows;i++)
  {
    string+="<tr>";
    for(j=0;j<7;j++)
    {
      if(j>dayinweek&&day==0) day=1;
      string+="<td onclick='document.getElementById(\""+fieldid+"\").value=\""+((day>0&&day<=daysinmonth)?day+"."+(month+1)+"."+(year):"")+"\";document.getElementById(\""+id+"\").style.display=\"none\";'>"+((day>0&&day<=daysinmonth)?day:"")+"</td>";
      if(day>0) day++;
    }
    string+="</tr>";
  }
  string+="</table>";
  document.getElementById(id).innerHTML=string;
  document.getElementById(id).style.display='block';
}