Among the employees who were born before 1969, what is the work shift of the 6th oldest employee?
oldest employee born before 1969 refers to year(BirthDate)<'1969';
SELECT T3.StartTime, T3.EndTime FROM Employee AS T1 INNER JOIN EmployeeDepartmentHistory AS T2 ON T1.BusinessEntityID = T2.BusinessEntityID INNER JOIN Shift AS T3 ON T2.ShiftId = T3.ShiftId WHERE STRFTIME('%Y', T1.BirthDate) < '1969' ORDER BY T1.BirthDate LIMIT 5, 1