user: Question: What Date has a Winning driver of Ugo Sivocci?
Columns: ['Name', 'Circuit', 'Date', 'Winning driver', 'Winning constructor', 'Report']
Types: ['text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['Targa Florio', 'Madonie', '15 April', 'Ugo Sivocci', 'Alfa Romeo', 'Report']
SQL:

assistant: SELECT "Date" FROM "Table" WHERE "Winning driver" = 'Ugo Sivocci';