Membership products can be enabled to expire on a given date. They can also be prorated if a Renewal Date is set.
For Yearly Memberships, you can pick a month and day that the membership will expire. The membership expires at the end of the day selected.
For Monthly Memberships, pick a day only. If you choose the 31st as the "Expires On" date, then the membership will use the maximum number of days in that month.
Prorating will adjust the price of the membership to the number of days received.
Auto Renew will create a new membership on the day after the "Expires On" date has passed.
For Daily Memberships, no membership renewal date is allowed to be set.