Add a 'date submitted' field to timesheet

It is hard to capture timesheets if they are submitted retrospectively. We run a query of timesheets for payroll each month but if someone has submitted for a previous month, we have to reconcile to know what has already been paid and what is new. If we could run the query on 'date submitted' rather than the date of the timesheet, this problem would be alleviated and save a lot of time.