user: Question: What date is the Portuguese Grand Prix?
Columns: ['Grand Prix', 'Date', 'Location', 'Pole Position', 'Fastest Lap', 'Winning Driver', 'Constructor', 'Report']
Types: ['text', 'text', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['Brazilian Grand Prix', '3 April', 'Jacarepaguá', 'Ayrton Senna', 'Gerhard Berger', 'Alain Prost', 'McLaren - Honda', 'Report']
SQL:

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