How to calculate Sum of Daily Active Users?

Hey guys,

quick DAX question. I have two tables, one table with users (two columns: users[id], users[name]) and another table with actions (actions[date], actions[user_id]). Besides that I have a calendar table.

Now I want to calculate the number of "active users", meaning the number of users who are active per time frame. That's pretty easy via:

Active Users = 
CALCULATE(
	COUNTROWS(users),
	FILTER(users,
		CALCULATE(
			COUNTROWS(actions), 
			FILTER(ALL(actions), 
				actions[user_id] = users[id] &&
				actions[date] >= MIN(calendar[Date]) &&
				actions[date] <= MAX(calendar[Date])
			)
		) > 0
	)
)

But if I want to calculate the number of "Daily Active Users" per time frame, meaning the Sum over the number of days one user is active per time frame over all users, I don't have any clue how to do that in a measure without creating an extra Crossjoin table between the users table and the calendar.

Any clues?

Thank you,

Sebastian