Data points at irregular time intervals

HTML

<script type="text/javascript" src="http://www.amcharts.com/lib/3/amcharts.js"></script>
<script type="text/javascript" src="http://www.amcharts.com/lib/3/serial.js"></script>
<script type="text/javascript" src="http://www.amcharts.com/lib/3/themes/none.js"></script>
<div id="chartdiv"></div>

CSS

#chartdiv {
	width	: 100%;
	height	: 500px;
}

JavaScript

var chart = AmCharts.makeChart("chartdiv", {
        "type": "serial",
        "theme": "none",
        "pathToImages": "http://www.amcharts.com/lib/3/images/",
        "dataDateFormat": "YYYY-MM-DD",
        "valueAxes": [{
           // "axisAlpha": 0,
            "position": "left"
        }],
        "graphs": [{
			"id": "g1",
            "bullet": "round",
            "bulletBorderAlpha": 1,
            "bulletColor": "#FFFFFF",
            "bulletSize": 5,
            "lineThickness": 2,
            "title": "red line",
            "useLineColorForBulletBorder": true,
            "valueField": "value"
        }],
        "chartScrollbar": {
			"graph": "g1",
			"scrollbarHeight": 30
		},
        "chartCursor": {
            "cursorPosition": "mouse",
            "pan": true
        },
        "categoryField": "date",
        "categoryAxis": {
            "parseDates": true,
            "dashLength": 1,
            "minorGridEnabled": true,
            "position": "top"
        },
        exportConfig:{
          menuRight: '20px',
          menuBottom: '50px',
          menuItems: [{
          icon: 'http://www.amcharts.com/lib/3/images/export.png',
          format: 'png'	  
          }]  
        },
        "dataProvider": [{
            "date": "2012-07-27",
            "value": 13
        }, {
            "date": "2012-07-28",
            "value": 11
        }, {
            "date": "2012-07-29",
            "value": 15
        }, {
            "date": "2012-09-18",
            "value": 47
        }, {
            "date": "2012-09-19",
            "value": 55
        }, {
            "date": "2012-09-20",
            "value": 59
        }, {
            "date": "2012-09-21",
            "value": 58
        }, {
            "date": "2012-09-22",
            "value": 57
        }, {
            "date": "2012-09-23",
            "value": 61
        }, {
            "date": "2012-09-24",
            "value": 59
        }, {
            "date":...