This context comes from the book "Outliers" by Malcolm Gladwell.
If you're too old in nineteen seventy-five, then you'd already have a job at IBM out of college, and once people started at IBM, they had a real hard time making the transition to the new world.
The same usage appears just a paragraph later:
If you were more than a few years out of college in 1975, then you belonged to the old paradigm.
(Wiktionary)
out (adverb):
(informal) Away, or at a distance, in time (relative to, and usually after, the present or a stated event) (often preceded by a stated time period and followed by "from")
Five years out from the passing of the law, nothing had actually changed.
The election is a long way out. (a long way in the future)