This is a tricky situation.

I am trying to subtract Holidays that I manually put into the shown Javascript in order to calculate the days a person is trying to request off.  I was able to get the script to remove weekends as well as half days from the form, but holidays are a whole other issue.

Attached is the script, along with an image of the form.

$(document).ready(function(){
  var holidays = ["2024-05-28", "2024-11-28", "2024-12-24", "2024-12-25", "2024-12-31"];
  function isCorrectDate(n) {
    var date = jQuery.datepicker.formatDate('yy-mm-dd', n);
    if (holidays.indexOf(date) != -1) {
        return false;
      } else {
        var t = n.getDay();
        return (t!=6 && t != 0);
      }
  }
  function checkDate(n) {
    return[isCorrectDate(n),""];
  }
  function checkField(input, inst) {
    if ($(input).closest('li').hasClass('checkDate')) {
      $(input).datepicker("option", {beforeShowDay: checkDate});
    }
  }
  $.datepicker.setDefaults( {beforeShow: checkField} );
  window.Parsley.addValidator('noweekend', {
    validateString: function(value) {
    console.log(value);
      return isCorrectDate(new Date(value));
    },
    messages: {
      en: 'Not valid date.'
    }
  });
  $('.checkDate input').attr('data-parsley-noweekend','');
})

function sumtotal() {
        var s = 0;
      	var e = 0;
  
      	//Get dates from input and reformat, then create date var
        $('.sdate input').each(function () {
          	s1 = $(this).val().replace("-", " ");
          	s2 = s1.replace("-", " 20");
            s = new Date(s2);
        });
      	$('.edate input').each(function () {
          	e1 = $(this).val().replace("-", " ");
          	e2 = e1.replace("-", " 20");
            e = new Date(e2);
        });
      
      var one_day = 1000 * 60 * 60 * 24;
      var startMillis = s.getTime();
      var endMillis = e.getTime();
      var totalDays = Math.round((endMillis - startMillis)/one_day);
      var weekend = 0;
      var days = 0;
      var holidays = 0;
      
      for (var i = startMillis; i < endMillis; i += one_day) {
        var currentDay = new Date(i);
        if (currentDay.getDay() == 5 || currentDay.getDay() == 6) {
          weekend++;
        }
      }
  
  	  //Check whether the half day radio button is "Yes"
  	  var choice = $('.halfday :checked').val();
        if (choice == 'Yes') {
          days = (totalDays+1) - 0.5 - weekend - holidays;
        } else {
		  days = (totalDays+1) - weekend - holidays;
        }
          
      		//Output value in the total class box
            if (isNaN(days)) {
      			$('.total input').val('Select dates');
            } else {
            	$('.total input').val(days);                
            }
      
     	if (e.getTime() < s.getTime()) {
	       	$('.edate input').val($('.sdate input').val());
        	sumtotal();
      	}
}

$(document).ready(function () {
  
    $(".sdate input").on('blur change', sumtotal);
  	$(".edate input").on('blur change', sumtotal);
  	$(".halfday input").on('blur change', sumtotal);  
    $(".read-only *").prop("readonly", true);

});