I know this is perhaps too late for you, but at least those who would run into this issue can find the fix here: first drag the desired date dimension onto Detail. Now, you need to make sure it is continuous, otherwise, it would show you "All" instead of the date range.
Hope this helps!
Old post, I know... while this does work, what I'm having trouble with is formatting it the way I'd like. It only works so far with exact dates, like 03/01/2014 to 03/31/2016. What I'd like is for it to say "March 2014 to March 2016". But when I try to get it to show up like that, it always ends up segmenting my line chart from a continuous line, breaking it up by month. Is there any way to format a continuous date differently in the title?
Brilliant! Works perfectly, thank you!!