In the first "Godfather" film, we see Vito Corleone's tombstone, and it says there that he was born on April 29. In this movie, however, Sonny curses the Japanese for bombing Pearl Harbor on Vito's birthday. The attack on Pearl Harbor happened on December 7, 1941.
At Michael's hearing, very few of the senators, judges, etc. are actually actors. They are friends, acquaintances, and family of various members of the cast and crew.