score:3

you can user series click event:

demo

series: {
    cursor: 'pointer',
    point: {
        events: {
             click: function() {
                 alert ('category: '+ this.category +', value: '+ this.y);
             }
        }
    }
}

score:4

if you use highstock then you can get x value (time in miliseconds) and use highcharts.dateformat() which return data in appropriate format. (http://api.highcharts.com/highstock#highcharts.dateformat())

http://jsfiddle.net/nx4kn/

 plotoptions: {
            series: {
                cursor: 'pointer',
                point: {
                    events: {
                        click: function () {
                            alert('date: ' + highcharts.dateformat('%y-%m-%d',this.x) + ', value: ' + this.y);
                        }
                    }
                }
            }
        }

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