I think this is my first crack at an advanced challenge and I have to say, what I did isn't pretty but I got the answer in the end. If for whatever reason you did download my solution, you'll see I then went back and did it a quicker, nicer, better way (hence why the workflow splits after the first filter).
I apologise to everyone who sees this:
This one took me hours to try and resolve... It was was certainly difficult and solution not pretty, but here it is...
PS. Be careful with one... I've seen a few solutions where the final result was actually incorrect (i.e. the wrong year calculated). It clearly is an advanced challenge!
Please let me know if you find any errors in my solution #alwayslearning