There are several types of calendars in the Jira calendar, and depending on these types, the permission settings are slightly different.
Now I will tell you everything:
Basic Calendar - Such a calendar does not use issues from Jira, so we just need to make sure:
Make sure the user has access to the application itself. You can do this here:
System-> Global Permissions-> Calendar UsersThe user you want to grant access to must be in this group.
Most likely all your users are in this group by default.Give the user one of the two calendar roles. Admin or User.
The admin can change the calendar, as well as add new events on the calendar. The user can only view the calendar.