JSFiddle - React, Tailwind, and code Playground

JavaScript

var date = "18/08/2011";
document.write("<b>Initial String: </b>" + date + " (european date) ");
var eurDate = date.substr(3, 2) + "/" + date.substr(0, 2) + "/" + date.substr(6);

document.write("<br /><b>To correct DateFormat #1: </b>" + eurDate);

var dattmp = "18/08/2011".split('/').reverse().join('/');
document.write("<br /><b>To correct DateFormat #2: </b>" + dattmp);

d = new Date(eurDate);
document.write("<br /><b>Converted #1: </b>" + d);

d2 = new Date(dattmp);

document.write("<br /><b>Converted #2: </b>" + d2);

var addedDate = new Date(d.setDate(d.getDate() + 1));

document.write("<br /><b>Add a day: </b>" + addedDate);

var month = addedDate.getMonth();
month++;
if(month < 10){
 month = "0"+month;
}
var theDateString = addedDate.getDate()  + '/' + month + '/' + addedDate.getUTCFullYear();

document.write("<br /><b>Result (back to String): </b>" + theDateString);