如何使用gRaphael线图设置x轴的日期值

<div id="chart-container"></div>

var paper = Raphael("chart-container", 800, 400);

function dateToTimestamp(dateString) {
  return new Date(dateString).getTime();
}

var x = [dateToTimestamp("2021-01-01"), dateToTimestamp("2021-01-10"), dateToTimestamp("2021-01-20")];
var y = [10, 30, 20];

var linechart = paper.linechart(10, 10, 700, 300, x, y, {});

linechart.axis({
  x: [dateToTimestamp("2021-01-01"), dateToTimestamp("2021-01-10"), dateToTimestamp("2021-01-20")],
  y: [0, 10, 20, 30],
  x_labels: ["2021-01-01", "2021-01-10", "2021-01-20"],
  y_labels: [0, 10, 20, 30],
});