var today = new Date();
var selectedDay = today.getDate();
var selectMonth =  today.getMonth()+1
function dateClick(_this){
    selectedDay = $(_this).html();
    refreshActivityList();
}
function refreshActivityList() {
    $('.day').html(selectedDay);
    $('.month').html(selectMonth+'月');
}

<meta charset="utf-8">
<link  rel="stylesheet" media="all">
<link rel="stylesheet" type="text/css" >
    <div id="calendar_1507462500931" class="ta_calendar ta_calendar2 cf" style="z-index: 9999; display: block; left: 0px; top: 35px;">
            <div class="ta_calendar_cont cf" id="dateRangePicker_1507462500931">
                <table class="dateRangeDateTable">
                    <caption>2017年10月</caption>
                    <thead>
                        <tr>
                            <th>S</th>
                            <th>M</th>
                            <th>T</th>
                            <th>W</th>
                            <th>T</th>
                            <th>F</th>
                            <th>S</th>
                        </tr>
                    </thead>
                    <tr>
                        <td id="calendar_1507462500931_2017-10-1" style="cursor: pointer;"><span onclick="dateClick(this);">1</span></td>
                        <td id="calendar_1507462500931_2017-10-2" style="cursor: pointer;"><span onclick="dateClick(this);">2</span></td>
                        <td id="calendar_1507462500931_2017-10-3" style="cursor: pointer;"><span onclick="dateClick(this);">3</span></td>
                        <td id="calendar_1507462500931_2017-10-4" style="cursor: pointer;"><span onclick="dateClick(this);">4</span></td>
                        <td id="calendar_1507462500931_2017-10-5" style="cursor: pointer;"><span onclick="dateClick(this);">5</span></td>
                        <td id="calendar_1507462500931_2017-10-6" style="cursor: pointer;"><span onclick="dateClick(this);">6</span></td>
                        <td id="calendar_1507462500931_2017-10-7" style="cursor: pointer;"><span onclick="dateClick(this);">7</span></td>
                    </tr>
                    <tr>
                        <td id="calendar_1507462500931_2017-10-8" style="cursor: pointer;"><span onclick="dateClick(this);">8</span></td>
                        <td id="calendar_1507462500931_2017-10-9" style="cursor: pointer;"><span onclick="dateClick(this);">9</span></td>
                        <td id="calendar_1507462500931_2017-10-10" style="cursor: pointer;"><span onclick="dateClick(this);">10</span></td>
                        <td id="calendar_1507462500931_2017-10-11" style="cursor: pointer;"><span onclick="dateClick(this);">11</span></td>
                        <td id="calendar_1507462500931_2017-10-12" style="cursor: pointer;"><span onclick="dateClick(this);">12</span></td>
                        <td id="calendar_1507462500931_2017-10-13" style="cursor: pointer;"><span onclick="dateClick(this);">13</span></td>
                        <td id="calendar_1507462500931_2017-10-14" style="cursor: pointer;"><span onclick="dateClick(this);">14</span></td>
                    </tr>
                    <tr>
                        <td id="calendar_1507462500931_2017-10-15" style="cursor: pointer;"><span onclick="dateClick(this);">15</span></td>
                        <td id="calendar_1507462500931_2017-10-16" style="cursor: pointer;"><span onclick="dateClick(this);">16</span></td>
                        <td id="calendar_1507462500931_2017-10-17" style="cursor: pointer;"><span onclick="dateClick(this);">17</span></td>
                        <td id="calendar_1507462500931_2017-10-18" style="cursor: pointer;"><span onclick="dateClick(this);">18</span></td>
                        <td id="calendar_1507462500931_2017-10-19" style="cursor: pointer;"><span onclick="dateClick(this);">19</span></td>
                        <td id="calendar_1507462500931_2017-10-20" style="cursor: pointer;"><span onclick="dateClick(this);">20</span></td>
                        <td id="calendar_1507462500931_2017-10-21" style="cursor: pointer;"><span onclick="dateClick(this);">21</span></td>
                    </tr>
                    <tr>
                        <td id="calendar_1507462500931_2017-10-22" style="cursor: pointer;"><span onclick="dateClick(this);">22</span></td>
                        <td id="calendar_1507462500931_2017-10-23" style="cursor: pointer;"><span onclick="dateClick(this);">23</span></td>
                        <td id="calendar_1507462500931_2017-10-24" style="cursor: pointer;"><span onclick="dateClick(this);">24</span></td>
                        <td id="calendar_1507462500931_2017-10-25" style="cursor: pointer;"><span onclick="dateClick(this);">25</span></td>
                        <td id="calendar_1507462500931_2017-10-26" style="cursor: pointer;"><span onclick="dateClick(this);">26</span></td>
                        <td id="calendar_1507462500931_2017-10-27" style="cursor: pointer;"><span onclick="dateClick(this);">27</span></td>
                        <td id="calendar_1507462500931_2017-10-28" style="cursor: pointer;"><span onclick="dateClick(this);">28</span></td>
                    </tr>
                    <tr>
                        <td id="calendar_1507462500931_2017-10-29" style="cursor: pointer;"><span onclick="dateClick(this);">29</span></td>
                        <td id="calendar_1507462500931_2017-10-30" style="cursor: pointer;"><span onclick="dateClick(this);">30</span></td>
                        <td id="calendar_1507462500931_2017-10-31" style="cursor: pointer;"><span onclick="dateClick(this);">31</span></td>
                    </tr>
                </table>
    </div>
    <div class="time-list non-activity" style="display: block;">
        <div class="time-item">
            <p class="time-month">
                <b class="day">11</b> <span class="month">10月</span>
            </p>
        </div>
    </div>
</div>
<script class="lazyload" src="data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAAAXNSR0IArs4c6QAAAARnQU1BAACxjwv8YQUAAAAJcEhZcwAADsQAAA7EAZUrDhsAAAANSURBVBhXYzh8+PB/AAffA0nNPuCLAAAAAElFTkSuQmCC" data-original="http://cdn3.maxuscloud.com/r/cms/pc/framework/jquery/jquery-3.1.0.min.js"></script>
<script type="text/javascript" class="lazyload" src="data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAAAXNSR0IArs4c6QAAAARnQU1BAACxjwv8YQUAAAAJcEhZcwAADsQAAA7EAZUrDhsAAAANSURBVBhXYzh8+PB/AAffA0nNPuCLAAAAAElFTkSuQmCC" data-original="newIndex.js"></script>