About how far into the future is the setting of Jimmy's world occurring?

Jimmy and Snowman share the same world for most of the novel. Much of it is told in flashback according to Snowman. In this sense, the novel is still in the not so distant future. There is no real time given to when Jimmy's world ends and Snowman's begins but judging from the intact infrastructure and even food that Snowman finds, it can't be that long.