CREATE TABLE table_30919 ("No. overall" FLOAT, "No. for series" FLOAT, "Title" TEXT, "Directed by" TEXT, "Written by" TEXT, "Original air date" TEXT, "UK viewers  ( million ) " TEXT)

What was the airdate of the episode with a UK viewership of 6.02 million?
SELECT "Original air date" FROM table_30919 WHERE "UK viewers (million)" = '6.02'
SELECT "Original air date" FROM "table_30919" WHERE "UK viewers (million)" = '6.02'