Forward to the part where N.Stahl is walking through the war room. You see Dell boxes all over the place. "These computers are least...30 years old!" The movie would predate to 1974 from the movie made. Altavista search says "Dell was founded in 1984 by Michael Dell, the computer industry's longest-tenured chief executive officer"
The original Terminator too place in 1984 (the year it was released). T2 was released 10 years later, but took place in 1997 (when Jon was 13). In T3, Jon makes reference to the events in T2 as happening "over 10 years ago." So we're at least to 2007, and entirely possible that it's at least 2014 (making your 30-year-old claim possible). More importantly, while the bunker itself may have been built and/or stopped general use 30 years prior, that doesn't mean it was completely abandoned. The facility still has power, the security codes for the main entrance were kept up to date, at least 2 trucks are seen in the entrance hangar, and Jon comments that the facility is a fallout shelter for big-wigs. So it's entirely possible (actually, probable) that the computer systems are periodically upgraded/replaced in order to remain functional.