What member selection function to use to always get a month of a previous year

Summary:

I am required to produce a financial report in Financial reporting web studio. in my Grid, I have account dimension selected for rows, company selected for page, and accounting period selected for columns. I have 4 columns for different accounting periods. I need to have 1 column with an accounting period which would always show December of the previous year based on accounting period current point of view selected by user. What function I can use to achieve this result?

Content (required):

Example: If user selects March 22, accounting period in the column should be December 2021. If user selects May 23, accounting period in the column should be December 2022