THE SETTING OF THE STORY

“...They went down toward the Seine, disgusted, shivering. Finally, they found on the Quai one of those old night-hawk cabs which one sees in Paris only after night has fallen, as though they are ashamed of their misery in the daytime...”

            So, as you’ve understood from the quotation  the events in the analyzed text take place in the glamorous city of lights and love, in Paris. I suppose it is the 19^th century. The importance Mathilde gives to money, posh "comfort," and fancy, fashionable baubles make her fit right in with the Paris of the late 19th century. That period was often called the "Belle Époque" (which you could translate as the "Lovely Age," or "Grand Years" – depending on how you understand it). It was a time of peace and technological innovation (electricity, for example). It was also a period of spectacular wealth, modish fashion, and what you might call "high consumerism."

But it’s only my presumption, as we don't get many specific clues or some details of clothes, of important people, places, or happenings of the time.  If the author doesn't give these details perhaps that doesn’t mean much. In such a way he draws our attention on that terrible event that happened in the life of ordinary french family. This makes the story immortal  and actual in all the times.