Precise calculation for "Years Employed" and "Years in Position"

Summary:

The client wants to add a "User-Defined Column" to calculate for the Business Unit Length of Service. They want to have the same calculation as the "Years Employed" and "Years in Position" has, which are delivered columns. Do we have a document or a guide on how "Years Employed" and "Years in Position" columns are calculated? So we can have the same calculation for the "User Defined Column" for Business Unit Length of Service. Thank you! ☺️