My first reaction, to be honest, was to be appalled. There’s no way that only a year and eight months has passed in the eight years since we began watching The Walking Dead, right? Twenty months? That’s it? How is it possible that so much has happened in only 90 weeks?
But putting aside the aging of the actors — Carl, in particular, who should have only been 13 on the series when he died — the rest of the timeline unbelievably seems to work, even taking into account the six-month time jump between seasons two and three. Here, however, is how Carl should have looked when he died at age 13, i.e., when the real-life Chandler Riggs was 13 years old.
The timeline also means that everything between the prison and the end of the All Out War happened in under one year, Day 300 to Day 632. They find the prison on Day 300; they discover Woodbury three days later; they live in the prison, vanquish the Governor, and see the prison fall over the course of seven months; Grady Memorial Hospital and Terminus happens over the next two weeks; and they arrive in Alexandria about 100 days before the current point in the series. Moreover, nearly the entire length of the All-Out War — two and a half seasons in real time — took place in basically a month, from Day 598 when Glenn is killed until today, Day 632.
It explains exactly why Maggie never showed because she was barely pregnant. It also means that Rick’s facial hair grows really fast. Rick had this beard on Day 514: