user: Question: What was the original air date of the episode that had 4.08 million U.S. viewers? 
Columns: ['No. in series', 'Title', 'Directed by', 'Written by', 'Original air date', 'Production code', 'U.S. viewers (millions)']
Types: ['real', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: [1.0, '" Pilot "', 'Jace Alexander', 'Matt Nix', 'June28,2007', 'BN100', '4.0']
SQL:

assistant: SELECT "Original air date" FROM "Table" WHERE "U.S. viewers (millions)" = '4.08';