We don’t know exactly how much time has passed on The Walking Dead, but we can make a rough estimate based on the timeline of events. Up through season five, about a year and a half had transpired, although — as of seven seven — it’s closing in on two years. (Interestingly, exposed to the open air, it takes about three years for a dead body to completely decompose, so at this rate, the majority of the world’s population who turned during the initial weeks of the outbreak will have completely decomposed by the 10th season).
In two years, Carl Grimes has had quite a growth spurt.
Maybe the zombie apocalypse just really ages kids? Except for the fact that in under two years, baby Judith hasn’t aged at an unnaturally fast rate.