What was the broadcast date of episodes that were watched by 23.2 million viewers?
CREATE TABLE "table1_27714985_1" (
  "no_s_in_series" real,
  "no_s_in_season" real,
  "title" text,
  "directed_by" text,
  "written_by" text,
  "original_air_date" text,
  "production_code_s" real,
  "u_s_viewers_millions" text
);
SELECT "original_air_date" FROM "table1_27714985_1" WHERE "u_s_viewers_millions"='23.2';