CREATE TABLE table_31388 ("Season" TEXT, "Season premiere" TEXT, "Season finale" TEXT, "TV season" TEXT, "Ranking" TEXT, "Viewers  ( in millions ) " TEXT)

What season was the finale that aired on May 23, 2004?
SELECT "TV season" FROM table_31388 WHERE "Season finale" = 'May 23, 2004'
SELECT "TV season" FROM "table_31388" WHERE "Season finale" = 'May 23, 2004'