GL Date in Transaction Window

Hi

I have a question on the Transaction's GL Date. Wehn i am entering the Transaction data in the Transactions Form, after savign the record my GL date is changing into the last day of that Period.

Example:

while entering the transaction XYZ,  i selected the GL Date as '15-OCT-2012'. But after saving the record, GL Date is updated to 31-OCT-2012 automatically.

Can some one please explain the reason and the setup which is causing this change in the GL date?

Thanks in Advance

Muralidhar Ng