user: Question: When is it has 15,557 Attendances?
Columns: ['Week', 'Date', 'Opponent', 'Result', 'Game site', 'Attendance']
Types: ['real', 'text', 'text', 'text', 'text', 'text']
Sample row: [1.0, '1963-09-08', 'at Boston Patriots', 'L 38–14', 'Fenway Park', '24,120']
SQL:

assistant: SELECT "Date" FROM "Table" WHERE "Attendance" = '15,557';