The Discount Days in the vendor setup (AP Setup, Vendors, Terms and Defaults tab) only calculates as days from the Invoice Date or the Date Received based on your selection in AP Settings, Invoice Settings.

At this time, for vendors with Discount Date terms that are for a specific day of the month or specific day of the following month, the Discount Date will have to be manually entered during the invoice entry.

Submit an enhancement request for additional Discount date options, similar to the Payment date options. To submit an enhancement request, in the software from the Help menu, select Web Resources, Submit Enhancement Requests.