JSFiddle - React, Tailwind, and code Playground

HTML

<input type="text" id="max_products" name="max_products" size="50"  >

JavaScript

//function to add days to a given date. 
  function addDays(startDate,numberOfDays)
  {
    var returnDate = new Date(
                startDate.getFullYear(),
                startDate.getMonth(),
                startDate.getDate()+numberOfDays,
                startDate.getHours(),
                startDate.getMinutes(),
                startDate.getSeconds());
    return returnDate;
  }


startingDate = new Date(2017,7,1)
 var adjustedDate = addDays(startingDate,13);
$('#max_products').val(adjustedDate);