Automatic filter of data from previous month

[Anonymous]

Hello together,

attached you see a screenshot of my starting page.

I included a button and tried to set an action to this button, so that everythime I push the button it automaticly sets the filter on the previous month. So if i push the button today i would like the filter to automaticly set 2017-09. If I push the button next month I would like to see the data of 2017-10, and so on.

I seen that the button has a field "Actions" where you can enter a formular. But so far I was not able to find the right syntax.

Any ideas?

Thanks in advance.

greetings