I am also new, just learning. I think you can add datatype.. 'timeofday' to your datatable, see the below sample.
eg: var data = new google.visualization.datatable();
data.addColumns('timeofday', 'TimeStamp'); // datatype, column label
data.addColumns('number', 'Consumers'); // datatype, column label
data.addRows([11,22,22],[10]); // [hours, min, sec] ,[consumers]
data.addRows([22,22,22],[15]);
var options ={} ;
var chart = new google.visualization.linechart(document.getelemntbyid("xx"));
chart.draw(data, options);