What is the repeat date of the episode that aired 22/12/1968?
CREATE TABLE "table1_13403120_1" (
  "num" real,
  "title" text,
  "director" text,
  "writer_s" text,
  "originalairdate" text,
  "repeatairdate_s" text,
  "prod_code" text
);
SELECT "repeatairdate_s" FROM "table1_13403120_1" WHERE "originalairdate"='22/12/1968';