title: Firebase track the time a user is logged in?
body: <p>In Firebase is there a way I can track the time a user is logged in?. I'm creating a student management app and I need to track the time a student is logged in, in order to mark them present. For example if a class is from 10:30 to 11:30 the student needs to be logged in for at least 50 minutes in order to mark them as present.</p>