CREATE TABLE table_56408 ("Race Name" CLOB, "Circuit" CLOB, "Date" CLOB, "Winning driver" CLOB, "Constructor" CLOB, "Report" CLOB)

Which date was the x gran premio di napoli?
SELECT "Date" FROM table_56408 WHERE "Race Name" = 'x gran premio di napoli'
SELECT "Date" FROM "table_56408" WHERE "Race Name" = 'x gran premio di napoli'