title: How can I make my timer keep running when the iPhone user quits to the home screen or the App Switcher?
body: <p>I'm making a quiz game and want to make sure that the user does not get additional answering time by exiting the app (without shutting it down).</p>
  <p>My current timer uses <code>Time.deltaTime</code>. I'm thinking of replacing this with something like <code>DateTimeOffset.Now.ToUnixTimeMilliseconds()</code> (epoch time) or <code>Time.realtimeSinceStartup</code> (not sure if this one works). A solution to detect when the user closes the app would also work.</p>