Platform: iOS / tvOS
To schedule the availability in the App Store, Apple gives you three options in the Version Release section:
Google Play Store
Platform: Android / Android TV
Currently, Android does not support scheduled releases. Still, Android supports Managed Publishing, where you have to press the Start rollout to production button to publish the App once the App has been reviewed and it is ready to publish. Also, it is possible to schedule when the following updates to the App will be released/published.
Platform: Samsung Smart TV
It is possible to schedule the App release in the last step of the Smart TV App Publication Process.
Platform: Amazon Fire TV
Amazon has recently added the ability to specify the date and time you would like your app to go live on the Amazon Appstore. This gives you the ability to coordinate your app release on Amazon with releases on other stores and in conjunction with any press or social media launch events you may wish to plan.
It is possible to schedule the App/Channel release in the Schedule Publishing option in the Developer Dashboard > Add Channel section.