JSFiddle - React, Tailwind, and code Playground

HTML

<form method="post" action="receive.js">
    <label for="checkin">Check-in Date:</label>
    <input type="text" name="checkin" id="checkin" placeholder="DD/MM/YYYY" pattern="(0[1-9]|[12][0-9]|3[01])\/(0[1-9]|1[0-2])\/\d{4}" />

    <input type="submit" value="submit" />

</form>