Refer below sample.
HTML
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.5.1/jquery.min.js"></script>
<script src="https://www.gstatic.com/charts/loader.js"></script>
<script>
    google.charts.load("current", { packages: ["timeline"] });
    function drawChart(data, chartDivId) {
        var container = document.getElementById(chartDivId);
        var chart = new google.visualization.Timeline(container);
        var dataTable = new google.visualization.DataTable();
        dataTable.addColumn({ type: 'string', id: 'Department' });
        dataTable.addColumn({ type: 'string', id: 'Event' });
        dataTable.addColumn({ type: 'date', id: 'Start' });
        dataTable.addColumn({ type: 'date', id: 'End' });
        for (var i = 0; i < data.length; i++) {
            dataTable.addRows([[data[i].Role, data[i].Name, new Date(data[i].starttime), new Date(data[i].endtime)]]);
        }
        var options = {
            timeline: {
                //groupByRowLabel: false // Display each event on a new line
            },
            height: 700,
        };
        chart.draw(dataTable, options);
    }
    $(document).ready(function () {
        $("#btnView").click(function () {
            var flightNo = $("#flightNo").val();
            var flightDate = $("#flightDate").val();
            var flightType = $("#flightType").val();
            $.ajax({
                type: "POST",
                url: "Default.aspx/GetChartData",
                data: JSON.stringify({ flightNo: flightNo, flightDate: flightDate, flightType: flightType }),
                contentType: "application/json; charset=utf-8",
                dataType: "json",
                success: function (response) {
                    drawChart(response.d, "departmentChartsContainer");
                },
                error: function (response) {
                    alert(response.responseText);
                }
            });
            return false;
        });
    });
</script>
<div id="registration-form">
    <div class='fieldset'>
        <legend>Clockify report!</legend>
        <div class="row">
            <div class="input-group">
                <asp:Label ID="Label1" runat="server" Text="Flight No" CssClass="label"></asp:Label>
                <asp:TextBox ID="flightNo" runat="server" CssClass="input"></asp:TextBox>
            </div>
            <div class="input-group">
                <asp:Label ID="Label2" runat="server" Text="Flight No" CssClass="label"></asp:Label>
                <asp:TextBox ID="flightDate" runat="server" CssClass="input"></asp:TextBox>
            </div>
            <div class="input-group">
                <asp:Label ID="Label3" runat="server" Text="Flight Type" CssClass="label"></asp:Label>
                <asp:DropDownList ID="flightType" runat="server" CssClass="input" Style="color: Black; font-size: 20px;">
                    <asp:ListItem Text="Arrival" />
                    <asp:ListItem Text="Departure" />
                </asp:DropDownList>
            </div>
            <!-- Add other input elements here -->
            <div class="input-group">
                <asp:Button ID="btnView" runat="server" Text="Submit" class="btn" />
            </div>
        </div>
    </div>
</div>
<!-- Container for department Gantt charts -->
<div id="departmentChartsContainer"></div>
Namespaces
using System.Data;
using System.Web.Services;
Code
[WebMethod]
public static List<ChartData> GetChartData(string flightNo, string flightDate, string flightType)
{
    List<ChartData> departmentChartData = new List<ChartData>();
    DataTable dt = new DataTable();
    dt.Columns.Add("ActionID");
    dt.Columns.Add("DeptName");
    dt.Columns.Add("eventname");
    dt.Columns.Add("starttime");
    dt.Columns.Add("endtime");
    dt.Rows.Add(1, "Caltering", "events bars1", new DateTime(2024, 2, 6), new DateTime(2024, 2, 10));
    dt.Rows.Add(2, "Caltering", "events bars2", new DateTime(2024, 2, 7), new DateTime(2024, 2, 11));
    dt.Rows.Add(3, "Caltering", "events bars3", new DateTime(2024, 2, 6), new DateTime(2024, 2, 13));
    dt.Rows.Add(4, "Airside", "events bars1", new DateTime(2024, 2, 6), new DateTime(2024, 2, 10));
    dt.Rows.Add(5, "Airside", "2", new DateTime(2024, 2, 7), new DateTime(2024, 2, 11));
    dt.Rows.Add(6, "Focc", "events bars4", new DateTime(2024, 2, 6), new DateTime(2024, 2, 13));
    dt.DefaultView.Sort = "DeptName";
    dt = dt.DefaultView.ToTable();
    foreach (DataRow dr in dt.Rows)
    {
        departmentChartData.Add(new ChartData
        {
            Role = dr["DeptName"].ToString(),
            Name = dr["eventname"].ToString() + " - " + dr["ActionID"].ToString(),
            starttime = dr["starttime"].ToString(),
            endtime = dr["endtime"].ToString()
        });
    }
    return departmentChartData;
}
public class ChartData
{
    public string Role { get; set; }
    public string Name { get; set; }
    public string starttime { get; set; }
    public string endtime { get; set; }
}
Screenshot
