It's possible to change the billing date for an active membership from a member's profile. For instance to give an extra week of gym access at no extra cost or to align their billing date with a date more suitable for them to pay.
If you're unable to edit the billing date, the membership may be cancelled or otherwise inactive.
Change the Billing Date for a Membership
Navigate to the member's profile (by searching for them in the search bar, for instance)
Select the Membership tab.
For the current membership, select the three dots next to the Billing.
Under Billing Date, select the new date.
Select Confirm.
Things to Consider When Changing Billing Dates
Changing billing dates affects the billing dates for all future payments. For example, if you change the billing date for a monthly membership from the 1st to the 2nd, all future payments will be taken on the 2nd.
If the new billing date is after the previous billing date, this will give the member extra time within the current billing period and no extra money will be collected. This means they could gain access to the gym for extra time.