As long as you have a paid subscription with us, you can access your previous schedule data as far back as you have entered it.
Just navigate to the week you want to view your old schedule, or use the REPORTS section to create various reports for any date range. Note that it is normally better to view past schedules using a view that is not listed by helper. For instance, if you use the Calendar Weekly, that view will also include shifts for deleted helpers.
You also can use the Schedule Search function to access shift information.