Reverse a Journal into a Prior Period option is disabled

Hi,
We have the following functional requirement:
The user needs to reverse a journal with a different period than the original journal. The reversed journal should be in an earlier period.
e.g. Original journal's period is 01-2014, and reversed journal should be 10-2013.

While reversing the journal, the user is able to select a period from the LoV, but valid periods in the list are only actual and future periods.

Referring to note "How To Reverse a Journal into a Prior Period? (Doc ID 1073616.6)" what the user needs to do is, select an earlier period through "Tools: Change Period" for the reversal journal. However this option is disabled in our R12 instance.