CREATE TABLE table_17600 ("Rank" FLOAT, "Fastest time  ( s ) " TEXT, "Wind  ( m/s ) " TEXT, "Athlete" TEXT, "Nation" TEXT, "Date" TEXT, "Location" TEXT)

Nigeria competed on July2, 1999.
SELECT "Date" FROM table_17600 WHERE "Nation" = 'Nigeria'
SELECT "Date" FROM "table_17600" WHERE "Nation" = 'Nigeria'