What date was the match against leonardo tavares with a score of 6–4, 6–4?
CREATE TABLE "singles_7" (
  "date" text,
  "tournament" text,
  "surface" text,
  "opponent" text,
  "score" text
);
SELECT "date" FROM "singles_7" WHERE "score"='6–4, 6–4' AND "opponent"='leonardo tavares';