Concurrent Usage by Month

I am trying to create a report that shows concurrent usage for one of our systems. We're only capturing session start times at the moment which means that we're having to add a variable to create what we think an average session lasts.


What I am struggling with is showing a distinct count of users in 20 minute intervals per day and month. If a user logged into the system at 10:30am, but then logged in again within a 20 minute window I only want to capture them once. I've tried grouping the data into intervals and adding a distinctcount but so far I've had no luck.

My data is setup as followed;

- Monthly Login Data - This shows all sessions with user details for each datetime

- Calendar - This is set up using a calculated table that looks at the minimum and maximum dates and times, and then also counts the minimum and maximum logins using this formula. =CALCULATE(COUNTA('Monthly Login View'[EmailAddress]),FILTER('Monthly Login View',AND([LoginDateTime]<=MAX('Calendar'[Date]),'Monthly Login View'[LogoutDateTime]>MAX('Calendar'[Date]))))

Is anyone able to advise of a way to go about this by either adding logic to the data I already have or by taking a new approach?

Thanks