It does not update on its own
Live updates in your own calendar
Download iCal: saves a one-off file that never updates. Useful if you want the fixtures on a single device, or would rather not have a live link.
Subscribe link: gives you a URL to add to your calendar (Google/Apple/Outlook). It updates itself — if a kickoff moves or a match is postponed, you will see it without doing anything.
Download the file once, or take a link that keeps itself up to date in Google and Apple Calendar.