CREATE TABLE table_23031 ("No. in series" FLOAT, "No. in season" FLOAT, "Title" CLOB, "Directed by" CLOB, "Written by" CLOB, "Original air date" CLOB, "U.S. viewers  ( millions ) " CLOB)

Name the original air date for 15.74 viewers
SELECT "Original air date" FROM table_23031 WHERE "U.S. viewers (millions)" = '15.74'
SELECT "Original air date" FROM "table_23031" WHERE "U.S. viewers (millions)" = '15.74'