How long until a newborn isn't classified as a newborn anymore? 1 month? 2? 3? I've no idea, inform me :D
I would say 3 months.
I would say after two months they're just a plain ol infant. :)
IMO I consider 4 months the end of it. That's when they really start to move around and grab things and awake a lot more and very aware.
Technically a baby is considered a newborn until their umbilical cord falls off, be that 2 weeks-4weeks then they are considered an infant.