CREATE TABLE table_24179 ("Episode" CLOB, "Broadcast date" CLOB, "Run time" CLOB, "Viewers  ( in millions ) " CLOB, "Archive" CLOB)

Which broadcast date has 6.8 million viewers?
SELECT "Broadcast date" FROM table_24179 WHERE "Viewers (in millions)" = '6.8'
SELECT "Broadcast date" FROM "table_24179" WHERE "Viewers (in millions)" = '6.8'