title: plotly js image markers on specific dates
body: <p>I'm using this example: <a href="https://plot.ly/javascript/images/#add-multiple-images" rel="nofollow noreferrer">https://plot.ly/javascript/images/#add-multiple-images</a> and trying to show image markers on specific dates.
  With xref set to "x", the images are not showing for x values like "1991-01-15".</p>
  
  <p>The images are showing if x axis is not dates as in the original example.</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-js lang-js prettyprint-override"><code>Plotly.plot('graph', [{
    x: ['1991-01-01', '1991-02-01', '1991-03-01'],
    y: [1, 2, 3]
  }], {
    images: [
    {
      "source": "https://images.plot.ly/language-icons/api-home/js-logo.png",
      "xref": "paper",
      "yref": "paper",
      "x": 0,
      "y": 1,
      "sizex": 0.2,
      "sizey": 0.2,
      "xanchor": "right",
      "yanchor": "bottom"
    },
    {
      "source": "https://images.plot.ly/language-icons/api-home/js-logo.png",
      "xref": "x",
      "yref": "y",
      "x": '1991-01-01',
      "y": 2,
      "sizex": 0.5,
      "sizey": 0.5,
      "xanchor": "center",
      "yanchor": "middle"
    },
  ]
  })</code></pre>
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;head&gt;
    &lt;script src="https://cdn.plot.ly/plotly-latest.min.js"&gt;&lt;/script&gt;
  &lt;/head&gt;
  &lt;body&gt;
    &lt;div id="graph"&gt;&lt;/div&gt;
  &lt;/body&gt;</code></pre>
  </div>
  </div>
  </p>