user: Question: What is the total number of Year(s), when Date (Opening) is "september 21"?
Columns: ['Year', 'Date (Opening)', 'Date (Closing)', 'Opening Film', 'Number of Screening']
Types: ['real', 'text', 'text', 'text', 'text']
Sample row: [2004.0, 'August 30', 'September 5', 'Deconstruction of Korean Housewife', '129 films 99 televised']
SQL:

assistant: SELECT COUNT("Year") FROM "Table" WHERE "Date (Opening)" = 'september 21';