When did the season premiere that saw 8.4 million viewers first air?
CREATE TABLE "ratings" (
  "season" text,
  "season_premiere" text,
  "season_finale" text,
  "tv_season" text,
  "ranking" text,
  "viewers_in_millions" text
);
SELECT "season_premiere" FROM "ratings" WHERE "viewers_in_millions"='8.4';