Deferred notifications tend to be confusing
When using a full-screen app, notifications tend to be deferred to when full-screen mode is quit. While this is an excellent sort of DnD (removes distractions), it is not indicated how long ago the notification was sent, which is often misleading especially for time-based notifications. It should be clearly indicated that the notification was pushed, say, "30 minutes ago", and possibly in a more visible way than the small time label in the calendar/notification list.