difference between columns in pivot table

I just did the years as an example.  In reality, none of the date logic helps me because Microsoft must work on a conventional calendar, so they've never been able to accomodate modern calendar innovations like a 13 month, or 32 day or 445.  Those columns can also be different regions like north east south west, or different teams of people like lakers, celtics.  The possibilities are many.  My sense is, no.  Microsoft doesn't have a concept that deals with data in the aggregate.  They want you to address it from the transaction up, which makes it twice as slow because if you want to do sales 2015 vs 2014, you'd have to pull it twice.  They probably have some patented concept to cache it magically rather than trust the user to just use the aggregated data explicitly.  Alas... Well, it is free...