The DVD timeline states Mary died in 1979. All of the (famous) real life events portrayed in Part III around the time of Mary's death happened in 1978.
The Immobiliare hearing took place in November, 1979, and apparently Mary died a few months later, so it appears to be 1980. But then again the poster for Anthony's opera makes it look like it was March, 1979, even though the opera opened after the Immobiliare hearing.
