What date was the match on a clay surface against Andrea Hlaváčková?
CREATE TABLE "itf_circuit_singles_finals_7_6" (
  "outcome" text,
  "date" text,
  "tournament" text,
  "surface" text,
  "opponent" text,
  "score" text
);
SELECT "date" FROM "itf_circuit_singles_finals_7_6" WHERE "surface"='clay' AND "opponent"='andrea hlaváčková';