What is the Date of the match with Opponent in the final Kenneth Carlsen?
CREATE TABLE "singles_18_12_6" (
  "outcome" text,
  "date" text,
  "championship" text,
  "surface" text,
  "opponent_in_the_final" text,
  "score_in_the_final" text
);
SELECT "date" FROM "singles_18_12_6" WHERE "opponent_in_the_final"='kenneth carlsen';