CREATE TABLE table_22438 ("Rank" FLOAT, "Title" TEXT, "Release Date" TEXT, "Franchise" TEXT, "Developer ( s ) " TEXT, "Platform" TEXT, "Units sold  ( in Millions ) " TEXT)

What day did the platform sell 9.87 million units?
SELECT "Release Date" FROM table_22438 WHERE "Units sold (in Millions)" = '9.87'
SELECT "Release Date" FROM "table_22438" WHERE "Units sold (in Millions)" = '9.87'