Using date name and datesinperiod

[benohara]

I'm missing something simple, please help!

I have a fact table and a date dimension linked on an integer surrogate key. The date dimension has the full date and also a Date Name column, so we can have slicers like "Today" and "Yesterday", and I can easily count how many events happened today

Calls Received = COUNTROWS('Fact Call Records')

 But when I'm trying to count how many happened in the last 30 days, I'm struggling.

Calls Received in Last 30 Days = 
    var SelectedDate = MAX('Dim Date'[FullDate])
    RETURN
    CALCULATE(
        'Fact Call Records'[Calls Received]
        ,DATESINPERIOD('Dim Date'[FullDate],SelectedDate,-30,DAY)
    )

works when FullDate is used as the slicer, but when I slice using DateName it returns the same as the single day count.

What am I missing?

[benohara · Accepted solution]

Typical, 9 minutes after posting I work out the solution. 

My date dimension wasn't marked as a date dimension. Right clicking on it and setting the full date field made it work as expected!