How to calculate total of hours worked in javascript?

See more:

C#

Javascript

ADO.NET

MVC5

Hi team

I dont know how to calculate total hours for user worked on a incident report, currently need some help around this logic. There are no errors and worked below does work and using ado.net to pull data back from table records. Should i need to have a unique record for total hours has datatype like datetime?

I am using visjs framework for timeline and here is the link below for documentation.
timeline - vis.js - A dynamic, browser based visualization library.[^]

What I have tried:

// Model

public class SelectOption
  {
      [Key]
      public int Incident { get; set; }

      public string Description { get; set; }


      public string Resources { get; set; }

      public DateTime Start_Date { get; set; }


      public DateTime Timestamp { get; set; }
  }

// Should i need to have a data type here for total hours?

// controller

  public TimeLineApplicationDBEntities2 _context = new TimeLineApplicationDBEntities2();
        public ActionResult Index()
        {
            return View();
        }

        public JsonResult GetAll()
        {
            var data = _context.Application_CheckList.ToList();
            return Json(data, JsonRequestBehavior.AllowGet);
}

// View.cshtml
<pre>@section scripts{

    <!-- CSS -->
    <script src="/vis/vis.js"></script>
    <link href="/Content/vis.min.css" rel="stylesheet" />

    <script type="text/javascript">

        $(document).ready(function () {


            $.ajax({
                type: "GET",
                url: "GetAll",
                contentType: "application/json; charset=utf-8",
                dataType: "json",
                success: ChartVis,
                error: OnError

            });


            function ChartVis(response) {
                // convert reponse to format being required by vis.js:
                const data = response.map((item) => {
                    // parse Start_Date in order to get pure timestamp:
                    const parsed = item.Start_Date.match(/\/Date\((\d+)\)\//);

                    // first attempt: create ISO date string, this was not necessary 
                    // as vis.DataSet accepts the timestamp:
                    // const start = new Date(Number(parsed[1]));
                    // const startStr = start.toISOString();

                    // return record in format being required by timeline
                    return { id: item.Incident, start: Number(parsed[1]), content: item.Description };
                });
                console.log(data);
                // DOM element where the Timeline will be attached
                var container = document.getElementById('visualization');

                // Create a DataSet (allows two way data-binding)
                var items = new vis.DataSet(data);

                // // Configuration for the Timeline
                var options = {};

                // // Create a Timeline
                var timeline = new vis.Timeline(container, items, options);
            }

            function OnError(response) {
                alert("Error !");
            }


        })

    </script>

}
<div id="visualization"></div>

}