Create new date range using parameter

Hello everyone,

In my workbook, I am trying to show YTD information based on a parameter month that the user can choose.

One of my views need to present trends that roles back 6 months. 

In the attached workbook (Super Store data), I created the Month parameter, when users select 12 (December 18) , I want the order date to roll back 6 months to August 18.

If users select 4 (April 18), order date will show data from December,17 to Apr,18....   

Would love to hear some ideas :-)

Thanks,

Yaron