If you have a customer who wants to change their 'Billing Date' on an auto-renew plan, you have an easy way to do that!
Log in to your business account.
Visit the 'Customers' page, and locate the customer you wish to adjust the billing date for. Click 'View', then at the bottom of the page, you will see details of the customer's auto renew membership under 'Auto-Renewing Plans'. Click the date link under 'Next Charge' column. The Edit Next Charge Date pop-up will appear where you can adjust customer's next renewal date using the date picker. Select customer's desired renewal date and then hit Save. (see screenshots below)
The new next charge date will apply on customer's next renewal. Then, each month, the customer will be automatically renewed 30 days from that point on.