JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.29.4/moment.min.js"></script>

JavaScript

moment.locale("pt", {
  week: {
    dow: 0
  }
})


const date = moment().year('2021').week(51).day('monday').format('YYYY-MM-DD');

console.log(date)