Montgomery Scott.
We speculate that Scotty was born in 2222.
This would make him 44, the same age as actor James Doohan during
the first season of the original Star Trek series (2266). Scotty served as
an engineering adviser on a couple of freighting runs to the miners in the
asteroid belt of the Denevan system ("Operation: Annihilate!" [TOS]).
This was apparently before his duty aboard the Enterprise (which began
around 2265). "Relics" (TNG) suggests that Scotty disappeared around 2294,
only to reappear in 2369. His disappearance had to occur after the launch of the
Enterprise-B, since he was a guest on that ship's first flight
(Star Trek Generations). We don't know what happened to
Scotty after he flew oft into the sunset aboard the Shuttlecraft
Goddard in 2369 ("Relics").
2222: Born ("Relics" [TNG]).
2240: Enters Starfleet Academy (conjecture).
2243:Begins serving as a Starfleet engineer ("Relics"
[TNG]).
2244: Graduates Starfleet Academy (conjecture).
2293: Attends launch of Enterpris B (Star Trek
Generations).
2294: Retires, is missing en route
to Norpin V colony ("Relics" TNG]).
2369: Discovered suspended in
transporter beam ("Relics" [TNG]).