CREATE TABLE table_24922 ("Round" FLOAT, "Circuit" TEXT, "Date" TEXT, "Pole Position" TEXT, "Fastest Lap" TEXT, "Winning Drivers" TEXT, "Winning Team" TEXT)

On how many different dates was the race at the Silverstone circuit?
SELECT COUNT("Date") FROM table_24922 WHERE "Circuit" = 'Silverstone'
SELECT COUNT("Date") FROM "table_24922" WHERE "Circuit" = 'Silverstone'