What dunfiddlin and I suggested would behave exactly the way you describe without having some kind of external source, or anything running in the background. The key question is whether or not the count reaching 0 should do anything when the app is not open. If the count reaching 0 should do something at all times, then the app would have to be running, which also means that the computer would have to be running. If you don't care about that, then what we were suggesting is that when the app shuts down, you stop the countdown (it will stop anyways because the app is no longer running), but you store enough information that you can re-start the countdown correctly when the app re-starts. Then, when you start up the app, it checks that stored information, figures out how much time has elapsed since the shutdown, and resumes the countdown at the point it would have reached had you not shut down the app.