amchart month column chart with date parsing

monthly_chart.html

<!-- Styles -->
<style>
#chartdiv {
  width : 100%;
  height  : 500px;
}

</style>

<!-- Resources -->
<script src="https://www.amcharts.com/lib/3/amcharts.js"></script>
<script src="https://www.amcharts.com/lib/3/serial.js"></script>


<!-- Chart code -->
<script>
function customLabelFunction(valueText, date, categoryAxis) {
  return (date.getMonth() + 1) + "/" + date.getFullYear().toString().substr(-2)
}

var chart = AmCharts.makeChart("chartdiv", {
    "type": "serial",
    "theme": "none",
    "marginRight": 40,
    "marginLeft": 40,
    "autoMarginOffset": 0,
    "mouseWheelZoomEnabled":false,
    "dataDateFormat": "YYYY-MM",
    "valueAxes": [{
        "id": "v1",
        "zeroGridAlpha": 1,
        "axisThickness": 0,
        "axisAlpha": 0,
        "gridCount": 0,
        "position": "left",
    }],
    "graphs": [{
        "type":"column",
        "id": "g1",
        "showBalloon":false,
        "bulletBorderThickness": 0,
        "bulletSize": 0,
        "maxBulletSize": 0,
        "minBulletSize": 0,
        "hideBulletsCount": 50,
        "lineThickness": 0,
        "fillAlphas": 1,
        "columnWidth": 0.75,
        "valueField": "value",
    }],
    "chartCursor": {},
    "categoryField": "month",
    "categoryAxis": {
        "parseDates": true,
        "axisAlpha": 0,
        "axisThickness": 0,
        "labelFrequency": 1,
        "minorGridAlpha": 0,
        "minorGridEnabled": false,
        "minPeriod": "MM",
        "labelFunction": customLabelFunction
    },
    "dataProvider": [{
        "month": "2012-07",
        "value": 13
    }, {
        "month": "2012-08",
        "value": 13
    }, {
        "month": "2012-09",
        "value": 35
    }, {
        "month": "2012-10",
        "value": 46
    }, {
        "month": "2012-12",
        "value": 66
    }, {
        "month": "2013-01",
        "value": 67
    }, {
        "month": "2013-02",
        "value": 64
    }, {
        "month": "2013-03",
        "value": 66
    }, {
        "month": "2013-04",
        "value": 60
    }, {
        "month": "2013-05",
        "value": 63
    }, {
        "month": "2013-07",
        "value": 61
    }, {
        "month": "2013-08",
        "value": 60
    }]
});


</script>

<!-- HTML -->
<div id="chartdiv"></div>