<tr class="table-header">で始まる日付部分を
<tr class="groupuser_timeline noselect">が続いている部分に3つ置きにjavascriptかjavaで挿入するにはどうすればいいでしょうか。

<tr class="table-header"> 
    <td class="col-user text-center">
     <button class="btn btn-default btn-sm" id="btn_today" onclick="todayClicked();" type="button">today</button>
    </td> 
    <td class="col-data">
     <div class="timeline"> <div class="cell"> <span class="select_day">6月5日(水)</span> </div> </div>
    </td>
</tr> 
<tr class="groupuser_timeline noselect" id="groupuser_timeline38950"> 
    <td class="col-user"> 
        <div class="calendar-param hidden" allmemberregistid="39950" calendarid="39950" displayname="name1" ownerid="38950"></div> 
        <div class="groupuser_data"> <dl class="user-table"><img alt="" src="/o/kview-scheduler-web/images/icon04.png"><span class="groupuser_user">name1</span>
        <dt class="user_post"><img alt="" src="/o/kview-scheduler-web/images/icon07.png"></dt>
        <dd class="user_post"><span class="position">position</span></dd>
        <dt class="user_division"><img alt="" src="/o/kview-scheduler-web/images/icon08.png"></dt>
        <dd class="user_division"><span class="department">department</span></dd> </dl> </div> 
    </td>
    <td class="col-data"> 
        <div class="timeline ui-droppable">
    </td> 
</tr>
<tr class="groupuser_timeline noselect" id="groupuser_timeline38951"> 
    <td class="col-user"> 
        <div class="calendar-param hidden" allmemberregistid="39951" calendarid="39951" displayname="name2" ownerid="38951"></div> 
        <div class="groupuser_data"> <dl class="user-table"><img alt="" src="/o/kview-scheduler-web/images/icon04.png"><span class="groupuser_user">name2</span>
        <dt class="user_post"><img alt="" src="/o/kview-scheduler-web/images/icon07.png"></dt>
        <dd class="user_post"><span class="position">position</span></dd>
        <dt class="user_division"><img alt="" src="/o/kview-scheduler-web/images/icon08.png"></dt>
        <dd class="user_division"><span class="department">department</span></dd> </dl> </div> 
    </td>
    <td class="col-data"> 
        <div class="timeline ui-droppable">
    </td> 
</tr>
<tr class="groupuser_timeline noselect" id="groupuser_timeline38952"> 
    <td class="col-user"> 
        <div class="calendar-param hidden" allmemberregistid="39952" calendarid="39952" displayname="name3" ownerid="38952"></div> 
        <div class="groupuser_data"> <dl class="user-table"><img alt="" src="/o/kview-scheduler-web/images/icon04.png"><span class="groupuser_user">name3</span>
        <dt class="user_post"><img alt="" src="/o/kview-scheduler-web/images/icon07.png"></dt>
        <dd class="user_post"><span class="position">position</span></dd>
        <dt class="user_division"><img alt="" src="/o/kview-scheduler-web/images/icon08.png"></dt>
        <dd class="user_division"><span class="department">department</span></dd> </dl> </div> 
    </td>
    <td class="col-data"> 
        <div class="timeline ui-droppable">
    </td> 
</tr>
<tr class="groupuser_timeline noselect" id="groupuser_timeline38953"> 
    <td class="col-user"> 
        <div class="calendar-param hidden" allmemberregistid="39953" calendarid="39953" displayname="name4" ownerid="38953"></div> 
        <div class="groupuser_data"> <dl class="user-table"><img alt="" src="/o/kview-scheduler-web/images/icon04.png"><span class="groupuser_user">name4</span>
        <dt class="user_post"><img alt="" src="/o/kview-scheduler-web/images/icon07.png"></dt>
        <dd class="user_post"><span class="position">position</span></dd>
        <dt class="user_division"><img alt="" src="/o/kview-scheduler-web/images/icon08.png"></dt>
        <dd class="user_division"><span class="department">department</span></dd> </dl> </div> 
    </td>
    <td class="col-data"> 
        <div class="timeline ui-droppable">
    </td> 
</tr>
<tr class="groupuser_timeline noselect" id="groupuser_timeline38954"> 
    <td class="col-user"> 
        <div class="calendar-param hidden" allmemberregistid="39954" calendarid="39954" displayname="name5" ownerid="38954"></div> 
        <div class="groupuser_data"> <dl class="user-table"><img alt="" src="/o/kview-scheduler-web/images/icon04.png"><span class="groupuser_user">name4</span>
        <dt class="user_post"><img alt="" src="/o/kview-scheduler-web/images/icon07.png"></dt>
        <dd class="user_post"><span class="position">position</span></dd>
        <dt class="user_division"><img alt="" src="/o/kview-scheduler-web/images/icon08.png"></dt>
        <dd class="user_division"><span class="department">department</span></dd> </dl> </div> 
    </td>
    <td class="col-data"> 
        <div class="timeline ui-droppable">
    </td> 
</tr>