What is the date that has yani tseng as the runner (s)-up?
CREATE TABLE "lpga_of_japan_tour_5" (
  "date" text,
  "tournament" text,
  "winning_score" text,
  "margin_of_victory" text,
  "runner_s_up" text
);
SELECT "date" FROM "lpga_of_japan_tour_5" WHERE "runner_s_up"='yani tseng';