How to retrieve the selected date range from relative date filter or date slicer

[imocean]

Hello everyone, my first question here hopefully a very basic one for many! 

I have a date filter in my report (in the relative mode so it's like 'last 3 months' etc.). Is there a way to retreive what's been selected in the filter in a measure so I can use it to do some calculations such as sales target etc.? I tried the formula below but it doesn't take the filter at all, instead it just gives me the total number of months in Date table regardless. 

SelectedNumberMonths = DATEDIFF(CALCULATE(MIN('Date'[Date]),ALLSELECTED('Date'[Date])), calculate(MAX('Date'[Date]),ALLSELECTED('Date'[Date])), Month)

And Date table is a table created to read calendar between 1/01/2001 and 31/12/2025. 

CALENDAR (DATE(2001,1,1), DATE(2025,12,31)

Thanks! 

[imocean]

Sorry for this but looks like working now after I added the slicer another time (rather than using the existing one - a bit weird). I will test further to make sure it's fully working though. Thanks anyway.