CREATE TABLE table_16287 ("Rnd" TEXT, "Race Name" TEXT, "Circuit" TEXT, "City/Location" TEXT, "Date" TEXT, "Pole position" TEXT, "Fastest lap" TEXT, "Winning driver" TEXT, "Winning team" TEXT, "Report" TEXT)

On how many dates did the Michigan International Speedway hold a round?
SELECT COUNT("Date") FROM table_16287 WHERE "Circuit" = 'Michigan International Speedway'
SELECT COUNT("Date") FROM "table_16287" WHERE "Circuit" = 'Michigan International Speedway'