I think using a parameter to select the year rather than a filter may be more beneficial in this example if I understand what you want correctly.
I have attached an example workbook which uses such.
Hope it helps!
Create a parameter that allows the user to select what year they want to treat as the current year. Then make a calculation that dynamically sets the PY for them as well.
IF YEAR([DateField]) = [ParameterYear] THEN 'Current Year'
ELSEIF YEAR([DateField]) = ([ParameterYear] - 1) THEN 'Previous Year'
ELSE 'Other Times'
You then can use this in the view and you can remove the 'other times' via the filters shelf. Further you then can use calculated field that works on top of this field.
SUM(IF [DateSorter] = 'Current Year' THEN [Value] END)
SUM(IF [DateSorter] = 'Previous Year' THEN [Value] END)
Which would give the difference between the two. Obvious you may want to do the quotient or the percent difference etc depending on your needs.
This is a very simplified exercise from the blog post that I wrote which you can find here: Date Comparisons in Tableau Made Easy
Have a look at this I have made a few amendments.
But I think the output is what you require.
Unfortunately I had to use a slider instead of options for years.
Hope this helps.
CY vs PY Comparison.twbx 6.5 MB