Which Date had an Opponent of buffalo bills?
CREATE TABLE "preseason" (
  "week" text,
  "date" text,
  "kickoff" text,
  "opponent" text,
  "result" text,
  "record" text,
  "game_site" text,
  "nfl_recap" text
);
SELECT "date" FROM "preseason" WHERE "opponent"='buffalo bills';