html - html表单验证消息自定义问题

Question

我试图更改表单验证消息自定义。但无法改变，总是给我一个“这个字段是必需的。 ”。我的html代码如下：

 <form id="UserSaveForm" method="post" class="form-horizontal" enctype="multipart/form-data" autocomplete="off">
 <div class="col-md- b-r" style="padding-right:30px;">
    <div class="form-group" id="data_1">
      <label class="font-normal">User Save Date</label>
         <div class="input-group date">
            <span class="input-group-addon"><i class="fa fa-calendar"></i></span>
             <input id="UserStartedDate" name="UserStartedDate" data-date-format="dd/mm/yyyy" data-date-end-date="0d" type="text"  class="form-control" required="" oninvalid="this.setCustomValidity('THİS İS MY CUSTOM VALİDATİON MESSAGE')"
                           oninput="setCustomValidity('')" >
         </div>
    </div>
 </div>
 <div class="form-group">
   <div class="col-sm-12">
        <div class="row">
           <button id="AddUser" type="button" class="btn pull-right btn-primary hidden" data-style="expand-right">Save</button>
        </div>
   </div>
 </div>
</form>