Which date had a year under 1988, loser of Philadelphia Eagles, location of Giants Stadium, and a result of 21-0?
CREATE TABLE "1980s_giants_12_9" (
  "year" real,
  "date" text,
  "winner" text,
  "result" text,
  "loser" text,
  "location" text
);
SELECT "date" FROM "1980s_giants_12_9" WHERE "year"<1988 AND "loser"='philadelphia eagles' AND "location"='giants stadium' AND "result"='21-0';