What is every original air date with U.S. viewers of 0.23 million?
CREATE TABLE "table1_29803475_2" (
  "no_in_series" real,
  "title" text,
  "directed_by" text,
  "written_by" text,
  "original_air_date" text,
  "u_s_viewers_million" text
);
SELECT "original_air_date" FROM "table1_29803475_2" WHERE "u_s_viewers_million"='0.23';