Field help (EXTDLVDAT) 

This is the delivery date calculated by the system taking into account the shipment date and delivery lead-time.  If the planned delivery date is modified, the system will suggest that the user modifies the shipment date as a function of the delivery lead-time.

During the modification of this date, the system controls that this date does not correspond to a non-working day or an unavailable day for the shipment date. If this is a non-working day, the date is postponed, otherwise a warning message is displayed.