How does the setting (time and place), impact the plot in The Giver?
The setting of this book has significant impact on the plot because it is the setting that helps to control the community.
The community is very isolated from the rest of the world, which they call "Elsewhere." Although there are neighboring communities, they all also prescribe to Sameness and are run by the same Council of Elders. So, the communities are very limited in their geographical scope, but also in their interaction with the rest of the world which has different beliefs than they do.
This community is very orderly, which at first doesn't seem too bad. As we learn more, though, it seems a bit too orderly and then it is obviously very controlled. This controlled setting literally constructs all of the characters in the story. They react to the rules they are given, and as a result none of them progress beyond one another. They all act according to the rules of their society and are products churned out by the community's rules. They have all agreed to Sameness, and we seen the people and the setting all conforming to this idea of uniformity.
We do not know when this story takes place - if this is in the past or in the distant future. We know they have the ability to genetically engineer their people, the weather, and their crops, so we can assume if this is in the past, it is not too long ago. The timeframe seems almost unimportant, as the message is timeless - question your surrounding and those who are in control of you and those surroundings!