title: Highcharts - with datetime axis labels overlap
body: <p>I'm using Highcharts and I have a chart with a datetime axis.
  Most times the labels are correctly distributed along the axis with no overlap.</p>
  
  <p>But sometimes it happens that labels overlap.
  Here you can see an example: <a href="http://jsfiddle.net/4ghhf/" rel="noreferrer">http://jsfiddle.net/4ghhf/</a>
  Using tickInterval and tickPixelInterval doesn't solve the problem.</p>
  
  <p>What should I do to avoid the problem?</p>