cdnで使用する
<script src="https://cdnjs.cloudflare.com/ajax/libs/date-fns/1.30.1/date_fns.min.js" integrity="sha512-F+u8eWHrfY8Xw9BLzZ8rG/0wIvs0y+JyRJrXjp3VjtFPylAEEGwKbua5Ip/oiVhaTDaDs4eU2Xtsxjs/9ag2bQ==" crossorigin="anonymous" referrerpolicy="no-referrer"></script>
dateFns が作成されるので、これを利用します。
console.log( dateFns.isToday(new Date()) );
console.log( dateFns.format(new Date(2017, 6, 6), 'MM/DD/YYYY') );
https://date-fns.org/v2.22.1/docs/format
console.log(d); // Wed Mar 09 2022 02:45:54 GMT+0000 (Coordinated Universal Time)
console.log(d.toLocaleString('ja-JP')); // 2022/3/9 2:45:54
console.log(d.toLocaleString("ja-JP", {timeZone: "Asia/Tokyo"})); // 2022/3/9 11:45:54