Hello I can help answer this question.
I am not sure I understand what you are asking so I will provide as much information as I think could answer it and if I am way off please let me know and I can provide more information.
How does multiple users of the calendar work? Do we have multiple logins and is there a way to see who does each entry on the calendar?
I am not sure if that is in reference to the Community Calendar or the regular calendar.
So I will answer for both.
Standard Calendar
All the events are controlled same as WordPress Post so each user who creates a post in an author.
Community Calendar for Front End Submissions
If you have anonymous submissions on each event goes to a default user for the site.
If you require users to be logged in, the event is tied to the account the user used to create the event.
Does that help?