During the creation and update of planned orders the Vendor Lead time should be considered when setting dates.

Consider this scenario:

There are two vendors that can deliver the same product, and both have purchase agreements. Planning is configured to choose the lowest price trade agreement. If a user wants to manually change the vendor on a planned order to the more expensive vendor that can delivery earlier the trade agreement for that vendor should be evaluated and the delivery date should update per that lead time.

This has been identified as a gap in:

859681 When creating manually a planned purchase order, Delivery date displayed does not consider purchasing lead time set on Default order settings

 Bug 951156 Changing the Vendor on a planned order does not trigger a recalculation of Requirement or Delivery date.