Hi STR
Do you work in US/ Latin America time zone. It is a common issue faced by users in these timezones as most of the systems for multinational environment are timed with GMT. So, let us say if you are creating a PO at 9-10 PM in your country, it is already the other day in Europe. This is just an example. Just try to check the system time of SAP using the system menu--> status from any screen of SAP and compare the time in your clock. It is possible the system time is much ahead and hence by the time you are creating the PO, it is other day in your system.
I had worked on these scenarios while working in Latin America. However, there was no feasible mechanism to log the current local time while creating PO (other than creating custom fields) . We cannot expect the PO document/creation dates to be entered in local time as that will create huge Havoc in the system. I guess your system is working fine and is just a time difference.
Regards
Vivek Singh