SAPF100 (f.05) : Reversal posting date is not correct

Dear Expert,

I have a problem on F.05 (Foreign Currency Valuation).

Parameters on posting are;

- Document date 30.06.2011

- Posting date 30.06.2011

- Reversal posting date 01.07.2011

- Reversal posting period 07

After executed batch input, FI document from the valuation is posted to 30.06.2011 (posting date is correct) but for reversal document posted to 31.07.2011 (posting date is not correct as I entered 01.07.2011).

Do you have any idea why such situation happen?

Thank you your help.

Phongthep N.