求 求 高手看jquery.ui.datepicker

这个日期控件有这个问题，只选择“年”(年的下拉列表)，日期不变化
非得选择“年” 再选择“月”日期框上才改变比如说，默认的月是5月，那选择哪一年，就应该变为哪一年的5月（不需要再选月了啊）
（因为，数据是不定在哪一天，所以没有数据的天就得是灰色的）不知道我表达的 大家能不能听懂？？谢谢大家了，给我看看吧...
下面是我的js文件 createDatePicker函数不太懂~~
var finished=true;
var currentYear=0;
var months={'date':['0000000000000000000000000000000', 
                    '0000000000000000000000000000000', 
                    '0000000000000000000000000000000', 
                    '0000000000000000000000000000000', 
                    '0000000000000000000000000000000', 
                    '0000000000000000000000000000000', 
                    '0000000000000000000000000000000', 
                    '0000000000000000000000000000000', 
                    '0000000000000000000000000000000', 
                    '0000000000000000000000000000000', 
                    '0000000000000000000000000000000', 
                    '0000000000000000000000000000000', ]};
var request;try {
        request = new XMLHttpRequest();
} catch (trymicrosoft) {
        try {
                request = new ActiveXObject("Msxml2.XMLHTTP");
        } catch (othermicrosoft) {
                try {
                        request = new ActiveXObject("Microsoft.XMLHTTP");
                } catch (failed) {
                        request = false;
                }
        }
}function nationalDays(date) {
var y=date.getYear();
var m=date.getMonth();
var d=date.getDate();

var currentMonth=months.date[m];
    var ch=currentMonth.charAt(d-1);
    if(ch=='0'){           
return [false,''];
    }
   return [true, ''];
}function updateInvalidDate() {
        if(request.readyState==4){
                months=eval(request.responseText);
                finished=true;                
                //alert(request.responseText);
        }
}function queryInvalidDate(year,func){
var current=window.location.href;
var pos=current.lastIndexOf("/");
var url=current.substring(0,pos)+"/GetInvalidDate.action?year=" + year;    
    finished=false;
    request.open("GET", url, true);
    request.onreadystatechange = func;
    request.send(null);
    //开始查询,        
    //alert(url);
}
function dp_onChangeMonthYear(y,m){
if(currentYear!=y){
/* alert("y="+y+" m="+m); */


queryInvalidDate(y,updateInvalidDate);
currentYear=y;
/*
alert('y='+y+' current='+currentYear); 
*/
}
}function createDatePicker(date1,date2){
var mindate=new Date(date1.substring(0,4), 1*date1.substring(5,7)-1, date1.substring(8,10));
var maxdate=new Date(date2.substring(0,4), 1*date2.substring(5,7)-1, date2.substring(8,10));
$('#datebox').datepicker( $.extend( {},
     $.datepicker.regional["zh-CN"], {  
         yearRange: '1900:2100',    
         minDate: mindate,
         maxDate: maxdate,
         beforeShowDay: nationalDays,
         onChangeMonthYear: dp_onChangeMonthYear,
         showOn: "both",
         closeAtTop: false,
         mandatory: true,
         changeFirstDay: false,
         onSelect: function(dateText) {$('#datepicker')[0].submit();},                  
         buttonImage: "images/calendar.gif",
         buttonText: "选择日期",     
         buttonImageOnly: true 
     })
         );  
}