title: Highcharts Uncaught TypeError: Cannot set property 'day' of undefined
body: <p>I have a highcharts chart that I'm trying to manually set the x axis label format on a click event using:</p>
  
  <pre><code>stockchart.xAxis[0].dateTimeLabelFormats.day = "%b %e";
  </code></pre>
  
  <p>However, I receive "Uncaught TypeError: Cannot set property 'day' of undefined". Can anyone explain what I'm doing wrong?</p>