JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://rawgit.com/dbushell/Pikaday/master/pikaday.js"></script>
<link rel="stylesheet" href="https://rawgit.com/dbushell/Pikaday/master/css/pikaday.css">
<input type="text" id="datepicker">

JavaScript

var picker = new Pikaday({
  field: document.getElementById("datepicker")
 ,onSelect: date=> {
    var year = date.getFullYear('2000')
       ,month = date.getMonth() + 1
       ,day = date.getDate()
       ,formattedDate = [
          year
         ,month < 10 ? "0" + month : month
         ,day < 10 ? "0" + day : day
        ].join("-")
    document.getElementById("datepicker").value = formattedDate
  }
})