Show user date of registration in user profile

functions.php

<?php

function show_user_date_of_registration( $user )
{
	$udata = get_userdata( $user->ID ); // user data
	$registered = $udata->user_registered; // user register date
	return date_i18n( "j M Y", strtotime( $registered )); // out
}

// Usage in author.php
$user = (isset($_GET['author_name'])) ? get_user_by('slug', $author_name) : get_userdata(intval($author));
echo show_user_date_of_registration($user);