Finding duration between two date. The calculation was made using JavaScript.

date_duration.html

      <div class="form-row" >
              <div class="form-group col-sm-4">
                <label class="font-weight-bold" for="pstatus">Estimated Start Date</label>
                <input type="date" class="form-control form-control-sm" name="estStart" id="estStart" data-group="section-b1">
         
              </div>
              <div class="form-group col-sm-4">
                <label class="font-weight-bold" for="ptype">Estimated End Date</label>
                <input type="date" class="form-control form-control-sm" data-group="section-b1" name="estEnd" id="estEnd" placeholder="Please enter the estimated end date">
              </div>
               <div class="form-group col-sm-4">
                <label class="font-weight-bold" for="ptype">Estimated duration (Days)</label>
                <input type="number" class="form-control form-control-sm" data-group="section-b1" name="estCmp" id="estCmp">
              </div>
      </div>
      
      <script>
      $(document).ready(function(){
          $("#estEnd").on("change", function () {
            var strdate = new Date($("#estStart").val());
            var enddate = new Date($(this).val());

            var timeDiff = Math.abs(enddate.getTime() - strdate.getTime());
            var diffDays = Math.ceil(timeDiff / (1000 * 3600 * 24));

            document.getElementById("estCmp").value = diffDays;
        });
      });
      </script>