Your church publishes a live calendar feed. A member subscribes once, your events appear in the calendar app they already use, and it stays current on its own.
This is not the same as "add to calendar", which copies one event across and then knows nothing about it afterwards. A subscription keeps up: change a time and their calendar changes too.
The link
Your feed lives at your church's own address, with /events.ics on the end. The
Add to Calendar button on your public Events section downloads a one-time
copy instead; to subscribe, use the link:
yourchurch.org/events.ics
If you have not connected a custom domain yet it is your
yourchurch.easychurchapp.com address instead. Either works.
What to tell members
iPhone: Settings → Calendar → Accounts → Add Account → Other → Add Subscribed Calendar, then paste the link.
Google Calendar: on a computer, next to "Other calendars" click + → From URL, then paste the link. It will not work from the phone app. Google only offers this on desktop, which is the single most common reason somebody says it did not work.
Outlook: Add calendar → Subscribe from web.
Where to put the link
Somewhere permanent, not in an announcement that scrolls away. A line on your events page ("Add our calendar to your phone") does more good over a year than any number of reminders.
What appears in it
Published one-off events, from about a year ago onward (up to 500). Drafts, scheduled-but-not-yet-published events and events marked Members Only are not in the feed, because the feed is public.
One thing to know before you promise anyone anything: recurring schedules (your weekly service) are not in the feed today, only one-off events.
If a member says an event is missing from their calendar, check whether it is actually published before looking for anything more complicated.
How fast it updates
Calendar apps decide that for themselves, and most check every few hours rather than instantly. It is the right tool for the shape of your month and the wrong one for telling people a service is cancelled this morning. That is a notification.