For the sake of completion, there are a few things that need to be talked about when implementing local notifications in Unity for the iOS target. The main one being the way Unity handles local notifications while the app is running: this done through this code in UnityAppController.
In this tutorial I will show you how to create an Android plugin to handle local notifications, the kind you need to dispatch after a delay or at a fixed interval.
The way to setup these notifications in Android is through the Alarm Manager. That way the system will take charge of the timing even if your game is not running.