CREATE TABLE table_72652 ("No. in series" FLOAT, "No. in season" FLOAT, "Title" TEXT, "Directed by" TEXT, "Written by" TEXT, "Original air date" TEXT, "Production code" FLOAT, "Viewers  ( millions ) " TEXT)

What is the original air date for the episode with a production code of 318?
SELECT "Original air date" FROM table_72652 WHERE "Production code" = '318'
SELECT "Original air date" FROM "table_72652" WHERE "Production code" = '318'