“When in Rome do as Romans do” it’s like “Paese che vai, usanze che trovi” in Italian. The short form is “when in Rome” But why we sai that? In 387 b.C. when St. Agostino arrived in Milan, he noticed that the local Church fasted on Saturday exactly like Roman Church because St. Ambrogio (bishop of Milan) wanted to follow the same traditions. St Ambrogio said “ When I’m in Rome I fast on Saturday, when I’m in Milan I follow the traditions oh the Church where I’m in”