how to fix this google charts bar chart error - google-visualization

Question

same data are used to draw line chart and bar chart. it works fine for drawing line. but there is an error for drawing bar chart. the error is "a.getTime is not a function×". any suggestions are appreciated.
here is my code:
datasource.addColumn('date', 'Date');
datasource.addColumn('number', 'quantity');
datasource.addColumn('number', 'quantity');
datasource.addColumn('number', 'quantity');
for (n = 0; n < tem.length; n++) {
datasource.addRows([[new Date(tem[n][0]), tem[n][1], tem[n][2], tem[n][3]]]);
}
*********line chart ***********
chart = new google.visualization.LineChart(document.getElementById('chart_div'));
var options = {
actions: ['dragToZoom', 'rightClickToReset'],
interpolateNulls: true, //bypass null
legend: 'none',
crosshair: { trigger: 'both', opacity: 0.5 }, // Display crosshairs on focus and selection.
title: 'Company Performance',
hAxis: { title: 'Year', titleTextStyle: { color: 'red' }, format: "YY.MM.dd", slantedText: true, slantedTextAngle: 30 },
vAxis: {
viewWindowMode: 'explicit',
viewWindow: {
max: maxy,
min: 0
}
},
explorer: { axis: 'horizontal', maxZoomOut: 1 } //wheel zoom
};
chart.draw(datasource, options);
***********bar chart*************
chart = new google.visualization.BarChart(document.getElementById('chart_div'));
var options = {
title: 'Company Performance',
hAxis: { title: 'Number', titleTextStyle: { color: 'red' } },
vAxis: { minValue: 0 },
explorer: { axis: 'horizontal', maxZoomOut: 1 }
};
chart.draw(datasource, options);*