The events in Chapter 7 of Donna Jo Napoli's Stones in Water probably take place in the latter half of 1941. Let's look at the evidence for this.
Roberto and Enzo are in the Ukraine, laboring to build an airstrip so that the Germans could land and refuel their planes after attacking targets in Russia. The boys have not been in this area very long, so the project is clearly a new one.
We know from history that Germany invaded the Ukraine as part of Operation Barbarossa, which started on June 22, 1941. By September, the Germans fully occupied the Ukraine and began using it as a base from which to strike into Russia. They would have needed airstrips immediately.
The chapter focuses on the cold weather where Roberto and Enzo are located, and Roberto reflects that winter comes early to this part of the Ukraine. This tells us that the month is probably October or even November, which would seem like early winter indeed to two young men from Venice.
We can infer, then, that the chapter probably takes place some time in the fall of 1941.