We have a requirement where we need to default the Need by Date as null when user enters check out page or Detail page for the first time in iProcurement, But the need by date is defaulted by (number of days setup in iProcurement Preferences for Need by Date offset)+sysdate. So we followed the below approaches but it didt' work
1. We set null for the profile values POR: Days Needed By and PO: Default Need-By Time then Need by date shows sysdate.
2. Extended the controller of the page and set null for Need by date column still showing sysdate.