The agenda widget on your Home Screen can display up to 6 of your next upcoming sessions in your personal schedule, depending on its size.
If a session in your personal schedule has already started, it will stay in the widget up to 5 minutes after the start time. After that point, it will no longer appear under your upcoming sessions.
As for how far ahead in your personal schedule the widget will show, it can be any length of time. That means even if the next session in your personal schedule is months away, it will still be listed in the widget!