CREATE TABLE table_2771 ("Episode" TEXT, "Location" TEXT, "Headliner" TEXT, "Comedians" TEXT, "Airdate" TEXT)

What date did the show air when Sean Lock was the headliner?
SELECT "Airdate" FROM table_2771 WHERE "Headliner" = 'Sean Lock'
SELECT "Airdate" FROM "table_2771" WHERE "Headliner" = 'Sean Lock'