Share an iCloud calendar. Tap Calendars, tap Edit, then tap the iCloud calendar you want to share. Tap Add Person, then enter a name, or tap 
to browse your Contacts. Those you invite receive an email invitation to join the calendar.
With Family Sharing, a calendar shared with all the members of your family is created automatically. See Family Sharing. You can also share an iCloud calendar with other iCloud users so they can view, add, and change events, and share a read-only version that anyone can view.
Create an iCloud calendar. Tap Calendars, tap Edit, then tap Add Calendar in the iCloud section.
Share an iCloud calendar. Tap Calendars, tap Edit, then tap the iCloud calendar you want to share. Tap Add Person, then enter a name, or tap to browse your Contacts. Those you invite receive an email invitation to join the calendar.
Change a person’s access to a shared calendar. Tap Calendars, tap Edit, tap the shared calendar, then tap the person. You can turn off their ability to edit the calendar, resend the invitation to join the calendar, or stop sharing the calendar with that person.
Turn off notifications for shared calendars. When someone modifies a shared calendar, you’re notified of the change. To turn off notifications for shared calendars, go to Settings > Notifications > Calendar > Shared Calendar Changes.
Share a read-only calendar with anyone. Tap Calendars, tap Edit, then tap the iCloud calendar you want to share. Turn on Public Calendar, then tap Share Link to copy or send the URL for your calendar. Anyone can use the URL to subscribe to the calendar using a compatible app, such as Calendar for macOS.