user: Question: How many different original air dates did the episode number 6 have? 
Columns: ['#', '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, '"A Love of a Lifetime"', 'Alex Graves', 'Kevin Falls', 'September24,2007', '1ANJ79', '9.16']
SQL:

assistant: SELECT COUNT("Original air date") FROM "Table" WHERE "#" = 6.0;