There were changes made to the date of termination (.DOT) at 7.30 and later at 7.60 and may have not been obvious to users unless they were running reports using that data item.
If an employee was entered in Classic, the .DOT was filled with 99/99/9999. If an employee was entered through the windows screens, the .DOT was filled with blanks. In either case, the employee would display a blank termination date in the 7.X window.

At 7.60, by design, the date should be 99/99/9999, but will still display with blanks.

To update all employees with blanks to have the 99/99/9999 date, in Division 00, System Utilities, with no one in Payroll execute
Program Name:  PYL916 Switches: Blank  Parameters: Blank.
Use the default Business Date and select your division, the select Run.

Any new employees entered on 7.60 will have the 99/99/9999 internally and on reports.
If .DOT is used in the employee selector, dates such as 01/01/1900 to the last real  termination date can be used to filter correctly.

Note: At 7.50 the 99/99/9999 could be removed. All you needed to do was go to the employee record click in the termination date field on the personal information tab (don't need to enter anything) and click ok
When running the user defined report again the 99/99/9999 goes away
This does not happen in 7.60, but it is by design. A new employee added in both Classic screens and in the windows screens will have the 99/99/9999 termination date.