title: Highstock highcharts irregular data gets wrong x-scale
body: <p>I have irregular data. Chart draws well when I use <strong>highcharts</strong>:</p>
  
  <pre><code>$(function() {
    var chart = new Highcharts.Chart({
      chart: {
        renderTo: 'chart'
    },
    xAxis: {
      type: 'datetime'
    },
    series: [{
      name: 'Volume',
      data: chart_arr,
    }]
  });
  });
  </code></pre>
  
  <p><a href="http://jsfiddle.net/KnTaw/9/">http://jsfiddle.net/KnTaw/9/</a></p>
  
  <p>But I have a lot of data so I need to zoom on the date and choose <strong>highstock</strong>. Then a strange thing happens: the x-axis become non-linear.</p>
  
  <pre><code>$(function() {
    var chart2 = new Highcharts.StockChart({
      chart: {
        renderTo: 'chart2'
      },
      rangeSelector: {
        selected: 0
      },
      xAxis: {
        type: 'datetime'
      },
      series: [{
        name: 'val',
        data: chart_arr,
        type : 'area',
      }]
    });
  });
  </code></pre>
  
  <p><a href="http://jsfiddle.net/Mc3mW/1/">http://jsfiddle.net/Mc3mW/1/</a></p>
  
  <p>Please note that the data for half an hour range Jan 6 20:00-20:30 allocates more space than 2 days Jan 11-13. (Of course the data is the same.)</p>
  
  <p>How can I force x-axis at highstock to become linear? Or How can I enable a bottom zoom tool for highcharts? Thank you.</p>