user: Question: Which date had a year under 1988, loser of Philadelphia Eagles, location of Giants Stadium, and a result of 21-0?
Columns: ['Year', 'Date', 'Winner', 'Result', 'Loser', 'Location']
Types: ['real', 'text', 'text', 'text', 'text', 'text']
Sample row: [1980.0, 'September 22', 'Philadelphia Eagles', '35-3', 'New York Giants', 'Veterans Stadium']
SQL:

assistant: SELECT "Date" FROM "Table" WHERE "Year" < 1988.0 AND "Loser" = 'Philadelphia Eagles' AND "Location" = 'Giants Stadium' AND "Result" = '21-0';