Highcharts: Dates Off By 1 Month

Question

I'm not sure what's going on, but dates are being displayed on the axis and in tooltips a month out. So the first date in data on this chart is in July but it shows up as in August and so on. Any ideas? I've put the code in a JSFiddle (http://jsfiddle.net/Z2VGL/1/) and also below:

$(function () {
$('#container').highcharts({
    chart: {
        type: 'spline'
    },
    title: {
        text: ''
    },
    plotOptions: {
        series: {
            lineWidth: 5,
            marker: {
                fillColor: '#FFFFFF',
                lineWidth: 2,
                radius: 6,
                lineColor: null // inherit from series
            }
        }
    },
    subtitle: {
        text: ''
    },
    xAxis: {
        type: 'datetime',
        dateTimeLabelFormats: { // don't display the dummy year
            month: '%e %b',
            year: '%b'
        }
    },
    yAxis: {
        title: {
            text: 'Ability Score (out of 100)',
            style: {
                color: '#323A45',
                fontWeight: 'bold'
            }
        },
        min: 0
    },
    tooltip: {
        formatter: function () {
            return '<b>' + this.series.name + '</b><br/>' + Highcharts.dateFormat('%e %b', this.x) + ': ' + this.y;
        }
    },

    series: [{
        name: 'Overall Ability',
        // Define the data points. All series have a dummy year
        // of 1970/71 in order to be compared on the same x axis. Note
        // that in JavaScript, months start at 0 for January, 1 for February etc.
        data: [
            [Date.UTC(2013, 07, 12), 50],
            [Date.UTC(2013, 08, 13), 57.9474605576],
            [Date.UTC(2013, 08, 14), 58.5667571154],
            [Date.UTC(2013, 08, 15), 69.0590308869], ]

    }, {
        name: 'Target',
        data: [
            [Date.UTC(2013, 07, 12), 80],
            [Date.UTC(2013, 08, 13), 80],
            [Date.UTC(2013, 08, 14), 80],
            [Date.UTC(2013, 08, 15), 80],
            /*
                    [Date.UTC(2013,  0,  1), 80.0],
                    [Date.UTC(2013,  1,  1), 80.0],
                    [Date.UTC(2013,  2,  1), 80.0],
                    [Date.UTC(2013,  3,  1), 80.0],
                    [Date.UTC(2013,  4,  1), 80.0],
                    [Date.UTC(2013,  5,  1), 80.0],
                    [Date.UTC(2013,  6,  1), 80.0],
                    [Date.UTC(2013,  7,  1), 80.0]
                    */

], dashStyle: 'longdash', marker: { enabled: false } }]

});

});

Thanks in advance.

Answer 1

As you can see from this doc: Mozilla JS Reference Date UTC

month
An integer between 0 and 11 representing the month.