function ChangeD(selobj){

  iYear=parseInt(document.getElementById(selobj + "_Y").value);
  
  if (iYear!=0){
	if (iYear<1911) iYear=iYear + 1911
	iMonth=parseInt(document.getElementById(selobj + "_M").value);

	var iday=0;

	switch (iMonth){

		case 1:
		  iday=31;
		  break;
		case 3:
		  iday=31;
		  break;
		case 5:
		  iday=31;
		  break;
		case 7:
		  iday=31;
		  break;
		case 8:
		  iday=31;
		  break;
		case 10:
		  iday=31;
		  break;
		case 12:
		  iday=31;
		  break;
		case 2:
		    var a=false;
		    if (iYear % 4==0){
		      a=true;
		      if (iYear % 100==0){
		        if (iYear % 400 !=0){a=false;}
		      }
		    }
	
		    if (a==true){
		      iday=29;
		    }
		    else
		    {
		      iday=28;
		    }
		  break;

		case 4:
		  iday=30;
		  break;
		case 6:
		  iday=30;
		  break;
		case 9:
		  iday=30;
		  break;
		case 11:
		  iday=30;
		  break;
	}	

	document.getElementById(selobj + "_D").length=iday+1;
	document.getElementById(selobj + "_D").options[0].value="";
	document.getElementById(selobj + "_D").options[0].text="";

	for (var i=1;i<=iday;i++){
		j=i;
		document.getElementById(selobj + "_D").options[i].value=i;
		if (i<10) j="0"+i;
		document.getElementById(selobj + "_D").options[i].text=j;
	}
  }
}

function ifChange(obj){
		ChangeD(obj);
}