Show Last 30 days data but user can change after applying Filter

 I want to create a dashbord which show last 30 days data by default. but as a user there should be option to select other months 

How to duplicate a column in table visual in tableau.

 

Refresh time in dashbord

 i want to show refresh time in dashbord based on user local time. Lets refresh done in 1 AM CET.

but when BST user open dashbord it should show BST time.