The Subscribe · .ics link downloads an iCalendar file of the community calendar. One-time setup, then your calendar app keeps the entries:

• Google Calendar: open Settings → Add calendar → From URL, paste https://quadruplicate.org/data/events.ics, and save. Google re-checks the file periodically.
• Apple Calendar (macOS/iOS): open File → New Calendar Subscription (or Settings → Calendar → Accounts → Add Account → Other → Subscribe to Calendar on iOS), paste the same URL, and confirm.
• Other apps: any client that supports “subscribe to calendar by URL” works with the same address; the direct file download is a fallback for one-time imports.