As long as Tableau is seeing your date as a real date it should be as easy as putting the discrete year on Color and the discrete month on Column and that will work.
The trick is when the data (years) are in 2 files. Are you UNIONing the 2 files together (ie they are the same format, number of columns, etc.. just have different years).
Right now these are in 2 files. And I don't believe I have anything Joined as I wasn't sure what to join on. Should I combine both files into one?
Sent from my iPhone
Yes, I'd definitely combine them Tableau can do this for you using the UNION if they are same/similar enough format or do it manually