You may have noticed that the WP Optin Wheel settings only allow to expire coupons X hours, minutes or days from the time it was won. If you don’t want that but you rather want all coupons to expire on a fixed date, you can add a piece of PHP code to your functions.php file:

add_filter('wof_woocommerce_coupon_data','wof_add_expiry_date');

function wof_add_expiry_date($data) {
   $data['expiry_date'] = strtotime('31 May 2020');
   $data['date_expires'] = strtotime('31 May 2020');
   return $data;
}

In the example above, all generated coupons will expire on May 31st, 2020.