'Return the datetime value to use as Schedule Date (``date_planned``) for the
Purchase Order Lines created to satisfy the given procurement.'

def _get_purchase_schedule_date(self):

    procurement_date_planned = datetime.strptime(self.date_planned, DEFAULT_SERVER_DATETIME_FORMAT)
    schedule_date = (procurement_date_planned - relativedelta(days=self.company_id.po_lead))
    return schedule_date
