What is the date where the attendance was 31,220?
CREATE TABLE table_56421 (
    "Date" text,
    "Opponent" text,
    "Score" text,
    "Loss" text,
    "Attendance" text,
    "Record" text
)
SELECT "Date" FROM table_56421 WHERE "Attendance" = '31,220'
Below are sql tables schemas paired with instruction that describes a task. Using valid SQLite, write a response that appropriately completes the request for the provided tables. ### Instruction: What is the date where the attendance was 31,220? ### Input: CREATE TABLE table_56421 (
    "Date" text,
    "Opponent" text,
    "Score" text,
    "Loss" text,
    "Attendance" text,
    "Record" text
) ### Response: SELECT "Date" FROM table_56421 WHERE "Attendance" = '31,220'