In Lois Lowry's young readers' novel The Giver, we are actually never told a name for the community nor told the age of the community. However, we certainly know the community is old enough to have raised and released at least a few generations. We know it is Jonas's friend Fiona's job to "release" the elderly from the community. We also know there are children in the community ranging in ages from infants, like Gabriel, and preadolescents, like Jonas and his friends, and there are parents in the community. Hence, the community is at least old enough to have raised three generations of the population, but that's only a minimum guesstimate.
By Chapter 18, in Jonas's conversations with the Giver, we also learn about a mistake the community made ten years ago that they call "the failure." Jonas asks the Giver to tell him the story of the failure and learns that Rosemary, who had been chosen to be the "the new Reciever," had been given memories that proved to be too overwhelming for her. She learned about loneliness, "poverty, and hunger, and terror" (p. 142). Eventually, she went to the Chief Elder and "asked to be released" (p. 143). Ever after that event, the elders made it a rule that the Receivers are forbidden to ask for release. Since we know the community made this mistake and changed the rules 10 years ago, we also know that the community is at least 10 years old, but again, due to the fact that it contains multiple generations, the community is probably much older than just 10 years old.
At best, we can speculate that the community is at least 10 to 80 years old and probably much older.