It should be able to alarm even when it isn't running. If you're seeing that it's not alarming, could you provide a little more info of what you tried and what didn't work? For example... created a non-repeating event at such and such time, checked alarm for 5 minutes early, hit apply, closed app, didn't see it. Another useful thing to know is if that behavior is repeatable for you or if sometimes it alarms and sometimes not. Your NIT OS version may be helpful too... can be found in Settings->Control Panel->About product, in the Version field.