Hi Zachary.Chen,

Zachary.Chen

But only the first series(i.e. series of index 0) got the right x values, the x values of other series seems to be set to the same random series that I don't know where it come from.

According to your description, I had written a demo on my computer.

I find if I don't set Series.XValueType to ChartValueType.DateTime,  it will show the result as image 2 shows.

So I suggest you change your codes and set  Series.XValueType to each series.

More details about my test demo, you could refer to follow codes:

Chart:

   <asp:Chart ID="Chart1" runat="server" Width="951px">
            <Series>
                <asp:Series Name="Series1"></asp:Series>
            </Series>
               <Series>
                <asp:Series Name="Series2"></asp:Series>
            </Series>
            <ChartAreas>
                <asp:ChartArea Name="ChartArea1"></asp:ChartArea>
            </ChartAreas>
              <ChartAreas>
                <asp:ChartArea Name="ChartArea2"></asp:ChartArea>
            </ChartAreas>
        </asp:Chart>

Code-behind：

protected void Page_Load(object sender, EventArgs e)
        {
            DataTable dt = new DataTable();
            dt.Columns.Add("weightNow", typeof(Int32));
            dt.Columns.Add("weightNow2", typeof(Int32));
            dt.Columns.Add("dateNow", typeof(DateTime));
            DateTime departure = new DateTime(2016, 5,1);
            DateTime arrival = new DateTime(2016, 6, 1);
            DateTime arrival2 = new DateTime(2016, 7, 1);
            DateTime departure1 = new DateTime(2016, 4, 1);
            DateTime arriva1l = new DateTime(2016, 3,1);
            DateTime arrival22 = new DateTime(2016, 2, 1);
            dt.Rows.Add(30,32, departure);
            dt.Rows.Add(42,36, arrival);
            dt.Rows.Add(54,38, arrival2);
            dt.Rows.Add(74,31, departure1);
            dt.Rows.Add(24,30, arriva1l);
            dt.Rows.Add(64,28, arrival22);
            //Chart1.DataBindTable(dt.AsDataView(), "dateNow");
            Chart1.Series["Series1"].ChartType = SeriesChartType.Column;
            //Chart1.Series["Series2"].ChartType = SeriesChartType.Column;
            //Chart1.Series["Series1"]["DrawingStyle"] = "Emboss";
 
            Chart1.DataSource = dt;
            Chart1.Series["Series1"].YValueMembers = "weightNow";
            Chart1.Series["Series1"].XValueMember = "dateNow";
            Chart1.Series["Series1"].XValueType = ChartValueType.DateTime;
            Chart1.Series["Series2"].YValueMembers = "weightNow2";
            Chart1.Series["Series2"].XValueMember = "dateNow";
            Chart1.Series["Series2"].XValueType = ChartValueType.DateTime;
            //Chart1.ChartAreas["ChartArea1"].AxisX.LabelStyle.Format = "yyyy-MM-dd";
            Chart1.Series["Series2"].ChartArea = "ChartArea2";
            Chart1.DataBind();
}

Best Regards,

Brando