calendar-element When confirm, it autoSubmit form about datetime-picker HOT 3 CLOSED

<div class="layout vertical">

  <iron-form id="form1" on-iron-form-submit="doSumit">
    <form action="/foo" method="get">
      name:
      <input name="name" value="Batman" />
      <br> job:
      <input name="job" value="Hero" />
      <br>
      <br> first day:
      <date-picker name="first" max="{{end}}" confirmed-value="{{start}}"></date-picker>
      <br> last day:
      <date-picker name="last" min="{{start}}" confirmed-value="{{end}}"></date-picker>
      <br>
      <br> last job:
      <datetime-picker name="lastjob" min="[[start]]" max="[[end]]" date="{{lastjob}}" property-for-value="datetime"></datetime-picker>
      <br> return:
      <time-picker name="return" min="[[lastjob]]" max="[[end]]" confirmed-value="{{return}}"></time-picker>
      <br>
      <br>
      <button on-click="form1submit">Submit</button>
      <button onclick="form1.validate()">Validate</button>
    </form>
    <div id="output"></div>
  </iron-form>

</div>