As The Giver (Lowry) begins, Jonas is eleven years old. We know this because he is looking forward to the Ceremony of Twelve. This ceremony takes place annually, as does the ceremony for all the children at their various ages.  There are no birthdays in the community, just this one day, which is a kind of coming-of-age ceremony for each age. The Ceremony of Twelve is particularly important, though, because it is when the Elders decide the career path for each child. These include everything from being a Fish Hatchery Attendant to being a Birthmother. As Jonas enters his twelfth year, he is chosen as the Receiver, the one to whom the Giver will pass on all the memories of past times and the memories of feelings that are no longer available to those in the community—love, for example, or pain. Once Jonas becomes the Receiver, he is considered twelve years old, and by the end of the book, there does not seem to have been enough time for him to have turned thirteen. There is no subsequent Ceremony in the book, so it seems safe to say he turns twelve in the book and remains twelve until its end.