Exchange rate date in PO's

What date field is used in the purchase order files to retrieve the currency exchange rate?

After analyzing our data, it appears to use the Price Effective Date (F4311.PDPEFJ).

I had been under the impression that for purchase order entry, the exchange rate is based on the order date field (PDTRDJ) and that the price effective date (PDPEFJ) is only used in calculations when the price at receipt processing option is turned on, then the GL date of receipt is used to get the effective price from the item master.

Can someone confirm?

Also on P4310, we have nothing set on the currency processing options.