This shows the timeline up to day 633, which is when they meet with Gregory to convince him to join the fight.
http://walkingdead.wikia.com/wiki/The_Walking_Dead_TV_Show_Timeline
Day 628 was eenie meanie miney moe day.
As for Judith, she was born on day 309. So up until the day they meet with Gregory, she is only 324 days old. The site doesn't go beyond day 633 so don't know how many days passed between that last day and last episode. Certainly not very long so Judith should only be a year old or just past a year old.
The amazing thing is, in 2 years, Carl has aged from 10 years old to 17 years old.