A subscription is valid for 1 month or 1 year, depending on the subscription type selected. Payment will be charged to your iTunes Account upon confirmation of purchase. Your subscription automatically renews unless auto-renew is turned off at least 24-hours before the end of the current period.
Your account will be charged for renewal at the price listed within 24-hours prior to the end of the current period.
Subscriptions may be managed and auto-renewal may be turned off via Settings > App and iTunes Stores > Apple ID > View Apple ID. No cancellation of the current subscriptions is allowed during active subscriptions period.