user: Question: On what date did Gunnar Nilsson make the fastest lap?
Columns: ['Race', 'Date', 'Location', 'Pole Position', 'Fastest Lap', 'Race Winner', 'Constructor', 'Report']
Types: ['text', 'text', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['Argentine Grand Prix', '9 January', 'Buenos Aires', 'James Hunt', 'James Hunt', 'Jody Scheckter', 'Wolf - Ford', 'Report']
SQL:

assistant: SELECT "Date" FROM "Table" WHERE "Fastest Lap" = 'Gunnar Nilsson';