CREATE TABLE table_11404452_1 (original_air_date VARCHAR, us_viewers__millions_ VARCHAR)

What is the original air date when there were 12.81 million u.s viewers?
SELECT original_air_date FROM table_11404452_1 WHERE us_viewers__millions_ = "12.81"
SELECT "original_air_date" FROM "table_11404452_1" WHERE "12.81" = "us_viewers__millions_"