Calculate days between two dates once checkbox is checked

Question

I am using below code which will count total days if cb1 is checked.

If cb1 is unchecked (default state) weekends will be excluded.

My 1st problem is that it is showing one day less in calculation once cb1 is checked and 2nd problem is that when cb1 is unchecked it is not showing any result.

Any help, please. I took reference from this thread.

(function () {
     if (getField("cb1").value != "Off") {
         var Start = this.getField("LeaveFrom").value;
         var End = this.getField("LeaveEnd").value;
         var dStart = util.scand("dd/mm/yyyy H:MM:SS", Start + " 0:00:00");
         var dEnd = util.scand("dd/mm/yyyy H:MM:SS", End + " 0:00:00");
         var diff = dEnd.getTime() - dStart.getTime();
         var oneDay = 24 * 60 * 60 * 1000;
         var days = Math.floor(diff/oneDay);
         event.value = days;
     } else {
         var start = this.getField("LeaveFrom").value; // get the start date value
         var end = this.getField("LeaveEnd").value; // get the end date value
         var start =util.scand("dd/mm/yyyy H:MM:SS", start + " 0:00:00");
         var end = util.scand("dd/mm/yyyy H:MM:SS", end + " 0:00:00");

         event.value = dateDifference(start, end);

         function dateDifference(start, end) {
             if (end < start) return -1;
             // Copy date objects so don't modify originals
             var s = new Date(+start);
             var e = new Date(+end);

             // Get the difference in whole days
             var totalDays = Math.round((e - s) / 8.64e7);
             // Get the difference in whole weeks
             var wholeWeeks = totalDays / 7 | 0;
             // Estimate business days as number of whole weeks * 5
             var days = wholeWeeks * 5;
             // If not even number of weeks, calc remaining weekend days
             if (totalDays % 7) {
                 s.setDate(s.getDate() + wholeWeeks * 7);
                 while (s < e) {
                     s.setDate(s.getDate() + 1);
                     // If day isn't a Friday or Saturday, add to business days
                     if (s.getDay() != 5 && s.getDay() != 6) {
                         ++days;
                     }
                 }
             }
             return days;
         }
     }
})();