DEMO CHART

HTML

<script src="https://rawgit.com/masayuki0812/c3/master/c3.js"></script>
<link rel="stylesheet" href="https://rawgit.com/masayuki0812/c3/master/c3.css">
<div id="chart" class="chart"></div>

JavaScript

var chart = c3.generate({
    data: {
 				x: 'x1', //remove this line
        xs: {
            'data1': 'x1',
            'data2': 'x2',
            'data3': 'x2',
            //'dataN': 'x2'
        },
        columns: [
            ["x1", "2013-12-30", "2014-01-06", "2014-01-13", "2014-01-20"],
            ["x2", "2015-01-05", "2015-01-12", "2015-01-19"],
            ['data1', 30, 150, 250, 100],
            ['data2', 20, 180, 190],
            ['data3', 40, 50, 190],
        ],
    },
    axis: {
        x: {
            type: 'timeseries',
            tick: {
                fit:false,
                format: '%Y-%m-%d'
            }
        }
    }
});