Usually, when any change in the master data is done for an employee, the date is updated in the Infotype 0003 in the field Ear. MD Change.
In our scenario, while running payroll it always start from 01.05.2006 even if we change the master data on some other date.
Note: All retiree employees have a Leaving Action record with the date after 10 years from the date of retirement.
If more information is needed, let me know.