You can download schedules from the schedule list. After setting the filters and clicking 'Get Schedules' to list the desired schedules, click the Excel image (outlined in red below) to download the listed schedules to a spreadsheet.
This list has future schedules and schedule history for about 4-5 years.
If you need older schedules and you are a sysop or have specific access to reports, you can go to Admin >> Reports >> Schedule Download. Then click 'Download Reports', set the criteria and press Download. This download has dates back to 2003.