function getBirthDayDateTime(year, month, day) {
    var now = new Date();
    var currYear = now.getFullYear();
    var currMonth = 1;
    var currDay = 1;
    var html = '';
    html += '<select  name="selYear" id="selYear" onChange="ChangeSelDay()">';
    for (var i = currYear; i > currYear - 60; i--) {
        html += '<option value="' + i + '"';
        if (i == year || (year==undefined && i==currYear-20))
            html += ' selected';
        html += '>' + i + '</option>';
    }
    html += '</select>年';
    html += '<select  name="selMonth" id="selMonth" onChange="ChangeSelDay()">';
    for (var i = 1; i <= 12; i++) {
        html += '<option value="' + i + '"';
        if (i == month || (month==undefined && i==currMonth))
            html += ' selected';
        html += '>' + i + '</option>';
    }
    html += '</select>月';  
    var dayCount = getCurrDayCount(year,month);
    html += '<select  name="selDay" id="selDay">';
    for (var i = 1; i <= dayCount; i++) {
        html += '<option value="' + i + '"';
        if (i == day || (day==undefined && i==currDay))
            html += ' selected';
        html += '>' + i + '</option>';
    }
    html += '</select>日';  
    document.write(html);
}

//改变年份和月份重新载入日期下拉
function ChangeSelDay(){
    var currYear = $('#selYear').val();
    var currMonth=$('#selMonth').val();
    var dayCount = getCurrDayCount(currYear,currMonth);
    var html='';
    for (var i = 1; i <= dayCount; i++) {
        html += '<option value="' + i + '">' + i + '</option>';
    }
    $('#selDay').html(html);
}

//获取当前年月的天数
function getCurrDayCount(year,month){
    var now = new Date();
    var currYear = year==undefined?now.getFullYear()-20:year;
    var currMonth = month==undefined?1:month;
    var dayCount = 30;
    switch (parseInt(currMonth))
    {
        case 1:
        case 3:
        case 5:
        case 7:
        case 8:
        case 10:
        case 12:
            dayCount = 31;    
            break;
        case 2:
            if((currYear%4 == 0 && currYear%100!=0) || currYear%400==0)
                dayCount = 29;
            else
                dayCount = 28;
            break;
    }
    return dayCount;
}