Current implementation of notification service does everything inside of on class which makes code hard to maintain. Such implementation should be refactored:
Logic of handling notifications should be separated from service
Preferences logic should be implemented as separate class which is passed to service on its creation(in fact such class is DAO-like interface for preferences)
Some functions like getDateTime should be moved to Utils
Current implementation of notification service does everything inside of on class which makes code hard to maintain. Such implementation should be refactored:
getDateTime
should be moved to Utils