CREATE TABLE table_39929 ("Date" TEXT, "Centerfold model" TEXT, "Interview subject" TEXT, "20 Questions" TEXT, "Pictorials" TEXT)

Which Date has a Pictorials of mercedes mcnab, girls of hawaiian tropic?
SELECT "Date" FROM table_39929 WHERE "Pictorials" = 'mercedes mcnab, girls of hawaiian tropic'
SELECT "Date" FROM "table_39929" WHERE "Pictorials" = 'mercedes mcnab, girls of hawaiian tropic'