function changeDay(i){
var html="";
	if(($("#month"+i).val() == 2)||($("#month"+i).val() == 4)||($("#month"+i).val() == 6)||($("#month"+i).val() == 9)||($("#month"+i).val() == 11)){
		html = html+"<select name=\"day"+i+"\">";
		for(j=1;j<=30;j++){
			html = html+"<option>"+j+"</option>";
		}
		html = html+"</select> 日 </span>";
		$("#day"+i).html(html);
	}else{
		html = html+"<select name=\"day"+i+"\">";
		for(j=1;j<=31;j++){
			html = html+"<option>"+j+"</option>";
		}
		html = html+"</select> 日 </span>";
		$("#day"+i).html(html);	
	}
}