Dates issue with Purchase Requisitions

Hi,

When generating Pur Req between 2 plants (one APO and other non APO), we are seeing a difference of dates in ECC and APO.

How is the transportation time calcuated for the Pur Req created and what is the relation of the transportation time to planned delivery time and GR/GI time maintained in info record or material master and means of transport maintained between these two locations in APO.

Which time is used for calculating the transportation time for a Pur Req?

Thanks,

Prash