Mostrar la fecha de registro de un usuario de WordPress sin plugins

				
					//fecha de registro
add_filter( 'manage_users_columns', 'rudr_modify_user_table' );
function rudr_modify_user_table( $columns ) {	
	// unset( $columns['posts'] ); // maybe you would like to remove default columns
	$columns['registration_date'] = 'Fecha de registro'; // add new
	return $columns;
}
add_filter( 'manage_users_custom_column', 'rudr_modify_user_table_row', 10, 3 );
function rudr_modify_user_table_row( $row_output, $column_id_attr, $user ) {	
	$date_format = 'd-m-Y';
	switch ( $column_id_attr ) {
		case 'registration_date' :
			return date( $date_format, strtotime( get_the_author_meta( 'registered', $user ) ) );
			break;
		default:
	}
	return $row_output;
}
add_filter( 'manage_users_sortable_columns', 'rudr_make_registered_column_sortable' );
function rudr_make_registered_column_sortable( $columns ) {
	return wp_parse_args( array( 'registration_date' => 'registered' ), $columns );
}