AlarmManager resets when the app starts.

I have an app whose AlarmManager resets when the app starts up again (ie, not just resume, but OnCreate runs again).

Case 1

I set the alarm to go off in 8 hours and I hit home to exit the app. I do not open the app again. The alarm works fine.

Case 2

I set the alarm to go off in 8 hours and I hit home to exit the app. I open the app after 5 hours. The alarm does not fire.

Is this normal behavior? How would I handle it?