Need to ensure a Power View report dynamically filters to the current month or year? One option is to add 'Current month' and 'Current year' calculated columns in Power Pivot which will update each time the model is refreshed

 

 

Then when visualizing with Power View just filter the data to the 'Current month'. The values for Current month will be updated whenever the data is refreshed - while will probably be regularly if you want to track a rolling window!