Simple Wordpress Page Reminder for registered user on your WP website.
User can set day of month (for example "5"), and time distance in months for example "6".
Now every 6 month on day 5, user receive email from your website about your next order for your products or services.
When today date is match with user date reminder, system automatically send email message and will change date for this user for his next remind.
Active PHP files based on WP page config. its no plugin.