Rolling Months on Pivots and KPIs


I have a question on how to update my KPI's where the data populates by month and will automatically start copying from the new month while dropping out an old month that is 13 months back? This will always show me the latest 12 months. I have multiple sites that I am running the reports from and would like to automate this to remove the hands on work on a monthly basis.

Any advice would be helpful. We are using the pivot app to pull and sort the data, but having the issue with mapping the new month. The above dashboard you see is only one of about 100 that are being tracked.

Thank you