SELECT date FROM table_name_68 WHERE year < 1988 AND loser = "philadelphia eagles" AND location = "giants stadium" AND result = "21-0"
Tanggal mana yang memiliki setahun di bawah 1988, pecundang Philadelphia Eagles, lokasi Stadion Giants, dan hasil dari 21-0?
CREATE TABLE table_name_68 (date VARCHAR, result VARCHAR, location VARCHAR, year VARCHAR, loser VARCHAR)