Article: Between the German invasion of Poland on 1 September 1939 and the Anglo-French declaration of War against the German Reich on 3 September 1939, the entire city (a total of 120,000 people) was evacuated, like other border towns as well. Until the arrival of the Wehrmacht troops mid-June 1940, the city was, for ten months, completely empty, with the exception of the garrisoned soldiers. The Jews of Strasbourg had been evacuated to Perigueux and Limoges, the University had been evacuated to Clermont-Ferrand.

Now answer this question: How long was the city completely empty?
ten months