user: Question: When was the Swiss Grand Prix?
Columns: ['Race', 'Circuit', 'Date', 'Pole position', 'Fastest lap', 'Winning driver', 'Constructor', 'Tyre', 'Report']
Types: ['text', 'text', 'text', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['Swiss Grand Prix', 'Bremgarten', '18 May', 'Giuseppe Farina', 'Piero Taruffi', 'Piero Taruffi', 'Ferrari', 'P', 'Report']
SQL:

assistant: SELECT "Date" FROM "Table" WHERE "Race" = 'Swiss Grand Prix';