Once the Expense Repot is converted to Invoice using the standard ‘Expense Report Export Program’ The invoice date is nothing but ‘week_end_date’ column populated on the ap_expense_report_headers_all table.
Below is the logic used behind the screens to populate ‘week_end_date’
1) If Expense Report Header is just entered and saved, the Expesne report header entry day will be the week_end_date
2) While entering an expense report line, you can select date on the expense report line: which is stored as expese_start_date
3) Also in the details when you enter No of days: expense_end_date will be calculated as expese_start_date+no.of.days
4) Once the expense_end_Date is populated, the weekend_date on the expense report header or Invoice_date, is nothing but the maximum value of the expense_end_Date of all lines.