skipped labels

HTML

<script src="http://code.highcharts.com/highcharts.js"></script>
<script src="http://code.highcharts.com/highcharts-more.js"></script>
<script src="http://code.highcharts.com/modules/exporting.js"></script>
<div id="container" style="height: 200px; min-width: 310px; max-width: 310px; margin: 0 auto"></div>

JavaScript

$(function () {
        $('#container').highcharts({
            chart: {
                type: 'column',
                borderColor: '#e2e2e2',
                borderWidth: 1,
                zoomType: 'xy',
                width: 800
            },
            title: {
                text: 'How can I stop it skipping date/time x axis labels?'
            },
            xAxis: {
                type: 'datetime',
                labels: {
                    step: 1,
                    maxStaggerLines: 1,
                    rotation: 90
                },
                startOnTick: false,
                tickInterval: 1000 * 60 * 60 * 24 * 30 ,
                min: Date.UTC(2012, 10, 1)
            },
            yAxis: {
                min: 0,
                title: {
                    text: 'Number of Cupcakes'
                },
                gridLineColor: '#e2e2e2',
                stackLabels: {
                    enabled: true,
                    style: {
                        fontWeight: 'bold',
                        color: (Highcharts.theme && Highcharts.theme.textColor) || 'gray'
                    }
                }
            },
            legend: {
                borderColor: '#e2e2e2',
                enabled: true,
                shadow: false
            },

            plotOptions: {
                column: {
                    pointRange: 1000 * 60 * 60 * 24 * 30 ,
                    stacking: 'normal',
                    dataLabels: {
                        enabled: true,
                        crop: false,
                        color: (Highcharts.theme && Highcharts.theme.dataLabelsColor) || 'white'
                    }
                }
            },
            series: [

            {
                name: 'Arthur',
                data: [
                    [Date.UTC(2012, 10, 1), 44],
                    [Date.UTC(2013, 3, 1), 16],
                    [Date.UTC(2013, 8, 1), 13]
                ]
          ...