SAMEPERIODLASTYEAR()

[procyon82]

I use

Revenue Last Year = CALCULATE(SUM('GA Ecommerce'[Revenue]),SAMEPERIODLASTYEAR('GA Ecommerce'[Date])) to create a column to have my last year's revenue in reference to what is displayed on my graph. That works beautifully!

I also added

Users Last Year = CALCULATE(SUM('GA Traffic'[Pageviews]),SAMEPERIODLASTYEAR('GA Traffic'[Date]))

and it doesn't work. It doesn't give an error, but simply stays blank.

Users Last Year = CALCULATE(SUM('GA Traffic'[Pageviews])

and

SAMEPERIODLASTYEAR('GA Traffic'[Date]))

each work separately though. Does anybody know what's wrong?