What is the intended date in the Expected Job End Date field in Job Data?

We have been using the Expected Job End Date field to track temporary employees when they are hired.   We have been entering the expected last day the employee will be working in that field.   When we go to terminate the employee and use the last day + 1 day as the effective date for the termination we receive the "Planned Exit Date cannot be before Job Effective Date" error message and not able to save the transaction.   In the past we have removed the Expected Job End Date date to save the transaction, knowing that information is in the hire row.   We have recently implemented Manager Self Service for these transactions and it errors out when we try to update the database, with this error message.