Problem in PGI date

Hi,

I am facing strange type of error in the delivery PGI date.

Delivery is created on 27 of september and the post goods issue is done on 29 september. Ideally the document should be posted on 29/10/2010, but the document was posted on 30/10/2010.

I thought the user might have changed it manually, but he didn't changed that one.

Could anyone please help me where could be the problem?

Thanks in advance

Regards,

CS