Table:
text: 1927 Grand Prix season
Other Grands Prix
Other Grands Prix
Name_ Circuit Date_ Winning_driver Winning_constructor Report
Tripoli Grand Prix Tripoli 6 March Emilio Materassi Bugatti Report
Opening Grand Prix Montlhéry 13 March Robert Benoist Delage Report
Pozzo Circuit Pozzo 20 March Gaspare Bona Bugatti Report
Provence Grand Prix Miramas 27 March Louis Chiron Bugatti Report
Targa Florio Madonie 24 April Emilio Materassi Bugatti Report
Messina Cup Messina 8 May Antonio Caliri Bugatti Report
Alessandria Circuit Alessandria 8 May Gaspare Bona Bugatti Report
Savio Circuit Ravenna 15 May Gaspare Bona Bugatti Report
Burgundy Grand Prix Dijon 27 May Raymond Leroy Bugatti Report
Perugia Cup Perugia 29 May Emilio Materassi Itala Report

Question: When did Gaspare Bona win the Pozzo Circuit in the 1927 Grand Prix season?