I had to go with 1-3 months though I don't know how accurate that assessment is. Basically, I found myself in a very violent environment and responded to that violence by developing 'survival' skills - staying away from home as much as possible. I don't know if that was PTSD or not - I think it was a beginning, though.
I quit sleeping (survival skill) but that wasn't because of nightmares until maybe five years later - when most danger had passed; then the nightmares started up in a major way.
I had severe startle reactions immediately but, again, I was in the middle of it. It never went away, though.
Staying away from groups was a learned survival skill at the time but I still can't stand them.
Where I used to be afraid to be at home, I turned into someone who 'protects' my territory beyond belief. I've known people for ten years or more who are not allowed in my space. If they showed up at my door one day, I wouldn't answer the door. As it is, if someone knocks on my door, I don't open it or acknowledge them.
Most people probably think I'm a little odd but they seem to have accepted my 'rules'. I think it's odd that they never ask. Of course, (knowing me) if they asked, we likely wouldn't be 'friends' - it's extremely rare for me to talk to someone about who and why I am.
So, it's a combination that, at the time probably looked like PTSD but I consider it simple survival skills that mutated. *shrugs*