A swishing, swirling gown is perfect for a late-night stroll. White silk organza V-neck halter gown with hand-beaded bodice, $4,600, by Liancarlo, 888-880-3462. Sterling silver and diamond chandelier earrings, $1,295; sterling silver, white gold and diamond overlapping cuff, $1,995, both by John Hardy, 787-754-0528 or reinholdjewelers.com. On him: Cream cotton and silk suit, $2,495; brown leather dress shoes, $395, both by Ermenegildo Zegna, 888-880-3462. White cotton pinstriped dress shirt, $450, by Ermenegildo Zegna Couture. Brown leather belt, $165, by Zegna Sport.