CREATE TABLE table_24194 ("No. in series" FLOAT, "No. in season" FLOAT, "Title" TEXT, "Directed by" TEXT, "Written by" TEXT, "Original air date" TEXT, "Production code" FLOAT, "U.S. viewers  ( millions ) " TEXT)

What date did episode 15 of the season originally air?
SELECT "Original air date" FROM table_24194 WHERE "No. in season" = '15'
SELECT "Original air date" FROM "table_24194" WHERE "No. in season" = '15'