Does the cancellation go into effect immediately?

Your subscription will remain in effect until the end of your current billing cycle.

• If you purchased on an iPhone, iPad, iPod Touch or AppleTV, go to the Manage Subscriptions section of your App Store account to see specifically when your subscription will expire
• On a Roku, go to Manage Subscription for the channel
• On an Android device, open the Google Play Store, tap Menu, Account, then Subscription. 
• If you purchased on historyvault.com, sign in to access your account and choose Billing History to see your next billing date