What was the date when Steffi Graf was the opponent in the final and the score was 2–6, 0–6?
CREATE TABLE "singles_37_19_18" (
  "outcome" text,
  "date" text,
  "tournament" text,
  "surface" text,
  "opponent_in_the_final" text,
  "score_in_the_final" text
);
SELECT "date" FROM "singles_37_19_18" WHERE "opponent_in_the_final"='steffi graf' AND "score_in_the_final"='2–6, 0–6';