What is the Date of the Tournament with a Winning score of −9 (65-71-68-67=271)?
CREATE TABLE "pga_tour_wins_7" (
  "date" text,
  "tournament" text,
  "winning_score" text,
  "margin_of_victory" text,
  "runner_s_up" text
);
SELECT "date" FROM "pga_tour_wins_7" WHERE "winning_score"='−9 (65-71-68-67=271)';