The Adjustment Period (13) for most needs to work so it is functionally useful.
The following is how I would like this to work - I believe the core code is there to work and just needs some tweaking...

1. To Create an Adjustment Period, the Start Date of the period (Last one listed) needs to be the Last Date of the Year;

2. On Financial Transactions and more advanced within the Project Accounting ML Module, the check box Adjustment Transaction, should be visible when this adjustment period date is selected (Last day of the year) but default is NOT checked;

3. When the Adjustment Transaction is not selected and the transaction is posted, then use the period before the adjustment period;

4. When the Adjustment Transaction checkbox is selected and the transaction is posted, then use the adjustment period

A more advance solution would be to have the ability to just have a checkbox when creating or calculating a Fiscal Period and having it as a yes/no so it creates this period automatically - this then solves the adjust the dates when doing this (Which is a pain)... It would also allow for the correct PERDENDT in the SY40100 table - for the pre-adjustment and adjustment periods