challenge in axis_x time format

This Sinppet of code results to an error:

var chart = c3.generate({
data: {
x: 'x',
// xFormat: '%Y%m%d', // 'xFormat' can be used as custom format of 'x'
columns: [
['x', '2013-01-04 23:12:00', '2013-01-03 23:12:00'],
// ['x', '20130101', '20130102', '20130103', '20130104', '20130105', '20130106'],
['data1', 30, 200, 100, 400, 150, 250],
['data2', 130, 340, 200, 500, 250, 350]
]
},
axis: {
x: {
type: 'timeseries',
max: '2013-01-05 23:12:00' ,
min: '2013-01-01 23:12:00',
tick: {
format: '%Y-%m-%d %H:%M:%S'
}
}
}
});

I have modifed this [example](http://c3js.org/samples/timeseries.html)
It seems the bug is related with max and min