Download is a one-off import of the fixtures. If the fixtures change, you will need to download the calendar file again to update your data. If you subscribe to the calendar feed, your calendar application will sync the fixture dates and kick-off times automatically without the need for a manual update so you will always have the latest information.
See instructions below for downloading or subscribing to your relevant calendar
Any calendar that works with iCal (.ics) or XML format, including: