=== modified file 'account_payment_discount_extension/account_payment_discount.py'
--- account_payment_discount_extension/account_payment_discount.py	2010-09-15 10:48:59 +0000
+++ account_payment_discount_extension/account_payment_discount.py	2010-09-15 14:57:36 +0000
@@ -47,7 +47,7 @@
                 payment_data = self.pool.get('account.payment.term').browse(cr, uid, inv.payment_term.id).cash_discount_ids
                 if payment_data:
                     delay = payment_data[0].delay
-                    self.write(cr, uid, [inv.id], {'next_payment_date':(datetime.now() + relativedelta(days=delay)).strftime('%Y-%m-%d')})
+                    self.write(cr, uid, [inv.id], {'next_payment_date':(DateTime.strptime(inv.date_invoice, '%Y-%m-%d') + DateTime.RelativeDateTime(days=delay)).strftime('%Y-%m-%d')})
         return data
         
     def _next_date(self, cr, uid, ids, context=None):