问如何返回正确的月份？

EN

var date = new Date("Tue Mar 28 2017 13:14:00 GMT+0100 (BST)");
var additionalMonth = date.getMonth();

function addZero(i) {
    if (i < 10) {
        i = "0" + i;
    }
    return i;
}

function formatDateToString(d){
    var month = '' + (d.getMonth() + 1);
    var day = '' + d.getDate();
    var year = d.getFullYear();
    var hour = d.getHours();
    var minute = d.getMinutes();
    var second = d.getSeconds();

    if (month.length < 2) month = '0' + month;
    if (day.length < 2) day = '0' + day;
    hour = addZero(hour);
    minute = addZero(minute);
	second = addZero(second);
	
	var date = [day, month, year].join('/');
	var time = [hour, minute, second].join(':');
	
	var newDate = date + " " + time;
	return newDate;
}

function setTimeForDate(date){
	date.setHours(12);
	date.setMinutes(0);
	date.setSeconds(0);
	return date;
}

function calculateDate(date, month){
	date.setMonth(month);
	date = setTimeForDate(date);
	return date;
}

function calculateLastDayMonth(date, day){
	var month = date.getMonth();
	var year = date.getFullYear();
	var d = new Date(year, month, 0).getDate();
	if(day >= d){
		date = new Date(year, month, 0);
	}
	date = setTimeForDate(date);
	return date;
}

function returnFormattedDate(startDate, additionalMonth){
	var day = startDate.getDate();
	var newDate = calculateDate(startDate, additionalMonth);
	var correctDate = calculateLastDayMonth(newDate, day);
	return formatDateToString(correctDate);
}

$(".returnedDate").text("START DATE: " + returnFormattedDate(date, additionalMonth));

for(var x = 0; x <= 5; x++){
  $("body").append(returnFormattedDate(date, additionalMonth) + "<br>");
  additionalMonth++;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.0/jquery.min.js"></script>
<h5 class="returnedDate"></h5>