The tasks that appear in the 'Upcoming' section are tasks that contain a date other than today or tomorrow. These tasks will automatically move up to 'Tomorrow' when tomorrow's date has been reached. If no date is set, it will move to tomorrow at the beginning of the week. The tasks that appear in the 'Someday' list are tasks that are not associated with a date.
Upcoming and Someday lists are viewable in 'Time View'. To view your tasks in 'Time View', please choose your desired list then tap on→ (Sort by:) and toggle it to 'Time' on the right- you will now see your tasks sorted by time.