Field help (DLVDAT) 

The delivery date corresponds to the date on which the goods will be received by the customer and the ownership transfer will be made. The search of the tax rates to apply is based on this date.
It is calculated from the Shipment date to which the Delivery lead-time has been added. This date can be modified.
In the case of an order delivery, if this date is changed, a message is displayed, proposing a new price list search when the user parameter SDHRECPRI - Order delivery price search (chapter VEN, SSD group) is set to ‘Yes’. When it is set to ‘No’, the price of the order is kept.
SEEINFOIf the calculated or entered delivery date corresponds to a non-working day defined in the customer delivery address, the delivery date is then automatically moved to the first working date following the initial delivery date.
If the calculated or entered delivery date corresponds to an unavailability period in the customer delivery address, a warning message signals it.