Set user registration date while creating account during Woocommerce order - wordpress

Question

When user completes the order, I want to save the user selected value as user registration date. I know it can be achived with this code:
wp_update_user(
[
'ID' => $user_id,
'user_registered' => $user->user_registered,
]
);
But how I can make it work with the rest of my code? How I can save this data as the registration date? I know how to save the order meta etc. but I've never did something like this.
add_action( 'woocommerce_before_checkout_registration_form', 'custom_checkout_fields_before_billing_details', 20 );
function custom_checkout_fields_before_billing_details(){
$domain = 'woocommerce';
$checkout = WC()->checkout;
echo '<div id="custom_checkout_field">';
woocommerce_form_field( '_custom_field_name', array(
'type' => 'text',
'label' => __('SELECT DATE', $domain ),
'placeholder' => __('DATE"', $domain ),
'class' => array('custom-field-class form-row-wide'),
'required' => false, // or false
), $checkout->get_value( '_custom_field_name' ) );
echo '</div>';
echo '<script>jQuery(document).ready(function( $ ) {$( "#_custom_field_name").datepicker();});</script>';
}
// Save custom checkout fields the data to the order
add_action( 'woocommerce_checkout_create_order', 'custom_checkout_field_update_meta', 10, 2 );
function custom_checkout_field_update_meta( $order, $data ){
if( isset($_POST['_custom_field_name']) && ! empty($_POST['_custom_field_name']) )
$order->update_meta_data( '_custom_field_name', sanitize_text_field( $_POST['_custom_field_name'] ) );
}
add_action( 'wp_enqueue_scripts', 'enqueue_datepicker' );
function enqueue_datepicker() {
if ( is_checkout() ) {
// Load the datepicker script (pre-registered in WordPress).
wp_enqueue_script( 'jquery-ui-datepicker' );
// You need styling for the date picker. For simplicity, I've linked to Google's hosted jQuery UI CSS.
wp_register_style( 'jquery-ui', '//code.jquery.com/ui/1.11.2/themes/smoothness/jquery-ui.css' );
wp_enqueue_style( 'jquery-ui' );
}
}