CREATE TABLE table_24831 ("Series #" FLOAT, "Season #" FLOAT, "Title" CLOB, "Directed by" CLOB, "Written by" CLOB, "Original air date" CLOB, "Production code" CLOB, "U.S. viewers  ( millions ) " CLOB)

How many original airdates did season 20 have?
SELECT COUNT("Original air date") FROM table_24831 WHERE "Season #" = '20'
SELECT COUNT("Original air date") FROM "table_24831" WHERE "Season #" = '20'