title: "Step" attribute not working on datetime-local
body: <p>I'm trying to use <code>datetime-local</code> to pick both date and time.</p>
  <p>The input works okay, unfortunately I can't seem to get the <code>step</code> attribute to work at all.</p>
  <p>The <a href="https://developer.mozilla.org/en-US/docs/Web/HTML/Element/input/datetime-local" rel="noreferrer">MDN docs</a> seem to suggest I should be able to use it to set a step in seconds, however <a href="https://codesandbox.io/s/priceless-silence-lt76h?file=/index.html" rel="noreferrer">this just isn't working at all</a>.</p>
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;form method='post' action='#'&gt;
      &lt;input
        type="datetime-local"
        id="meeting-time"
        name="meeting-time"
        value="2018-06-12T19:30"
        min="2018-06-07T00:00"
        max="2018-06-14T00:00"
        step="900"
      /&gt;
  &lt;input type='submit' value='Go!'&gt;
  &lt;/form&gt;</code></pre>
  </div>
  </div>
  </p>
  <p>Am I missing something?</p>