ParseDate output error

I am running Tibco Spotfire build version, build date 2/13/2015

I want to create a calculated column and the ParseDate function to transform a string to date format. 

The string is formatted as "yyyymmdd". My function reads: ParseDate([ProcessDate as String], "yyyymmdd", "en-US")

Output is in the format mm/dd/yyyy, and seems to return dd and yyyy correctly, but all mm are returned with value 01; i.e. string 20111231 transforms to 1/31/2011

How do I get this to output correctly?

(1) Answer