Add it once and it keeps itself up to date, including changes and approved swaps.
Calendar help
iPhone, iPad, Mac: tap Add to Apple Calendar, then Subscribe. It checks for changes on its own, usually within an hour. To check now, open Calendar, tap Calendars, and pull down.
Google Calendar: add it from a computer (Google's phone app can't add calendar links). It then shows up in the Google Calendar app on your phone. Google can take several hours, sometimes a day, to pick up changes.
Outlook or anything else: use Copy link and paste it where the app says "subscribe" or "add calendar from URL".
Shared the link by mistake? The old one stops working, so add the new one to your calendar again.