What is the date of the match against John McEnroe with a Score of 3–6, 6–3, 2–6?
CREATE TABLE "singles_finals_13_5_8" (
  "outcome" text,
  "date" real,
  "championship" text,
  "surface" text,
  "opponent" text,
  "score" text
);
SELECT "date" FROM "singles_finals_13_5_8" WHERE "opponent"='john mcenroe' AND "score"='3–6, 6–3, 2–6';