What is the date of the U.S. Women's open?
CREATE TABLE "lpga_tour_11" (
  "date" text,
  "tournament" text,
  "winning_score" text,
  "margin_of_victory" text,
  "runner_s_up" text
);
SELECT "date" FROM "lpga_tour_11" WHERE "tournament"='u.s. women''s open';