CREATE TABLE table_31057 ("Episode" FLOAT, "Airdate" CLOB, "Iron Chef" CLOB, "Challenger" CLOB, "Theme Ingredient" CLOB, "Winner" CLOB)

What date did the episode air when guy grossi won?
SELECT "Airdate" FROM table_31057 WHERE "Winner" = 'Guy Grossi'
SELECT "Airdate" FROM "table_31057" WHERE "Winner" = 'Guy Grossi'