user: Question: When was the F4 7 series?
Columns: ['Circuit', 'Location', 'Date', 'Series', 'Winning driver', 'Winning team']
Types: ['text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['Ciudad del Motor de Aragón', 'Alcañiz , Spain', '17 April', 'FR3.5 1', 'Mikhail Aleshin', 'Carlin']
SQL:

assistant: SELECT "Date" FROM "Table" WHERE "Series" = 'F4 7';