Set Default Date on PBGInvcGen

We use Project Billing and I need to change the default invoice date to match the period end date? We are on Epicor 10.2.100.17. For some backgound information, we invoice at the last day of the month. This month ended on a Sunday and when they created their invoices, they used the first, instead of the last day. They asked if we can change the invoice date to match the period end date (they always change this, but not always the invoice date).