A. A normal or disability pension shall commence the first day of the month following retirement. A preretirement survivor pension shall commence the first day of the month following the date of the death resulting in the pension. A postretirement survivor pension shall commence the first day of the month following the date of the death resulting in the pension.
B. Termination of payment of a pension shall occur at the end of the month in which the event causing termination occurs. Payment shall be made for the full month of termination.
C. A change in the amount of a pension shall occur the first day of the month following the date of the event causing the change.