CREATE TABLE table_16756 ("#" FLOAT, "Race Name" TEXT, "Circuit" TEXT, "Date" TEXT, "Winning driver" TEXT, "Constructor" TEXT, "Report" TEXT)

How many dates have silverstone circuit
SELECT COUNT("Date") FROM table_16756 WHERE "Circuit" = 'Silverstone'
SELECT COUNT("Date") FROM "table_16756" WHERE "Circuit" = 'Silverstone'