Ha, we kid about the 50-years thing: it was outdated by the 1980s, by which time most everybody else had migrated to relational databases. Still, Individual Master File managed to defeat all the billions of dollars and replacement projects the government could throw at it, trudging happily along and restricting the IRS from accessing individual files more often than once a week. It was only this year that Individual Master File was replaced by Customer Account Data Engine (CADE), a more conventional database system run on IBM hardware -- CADE 2, actually, because the original CADE was a failed project that was killed after years of development. And even that switchover was only for data for individuals; taxes for businesses and retirement plans are still kept on the old system for now.
Big Blue predicts blue skies
Sometimes longtime government use of technology isn't the result of chaos and incompetence, but simple thriftiness. When it comes to weather predictions, satellites and doppler radar get all the press, but the National Weather Service still relies on good old-fashioned balloons -- and much of the data sent from those balloons is still processed by good old-fashioned IBM PC XT machines, dating from the 1980s. It did turn out that 640KB wasn't enough for everybody, but it seems that it's still good for many purposes.
Future generations wonder: Wait, what did 'XP' stand for again?
If you want to find an archaic outdated operating system, maybe you need look no further than your desktop: after all, it's possible your PC is one of the 40.7 percent that still runs Windows XP. This is an operating system that was released in October of 2001 -- ten and a half years ago, as of this writing. To give you a sense of how long that span of time is (and to make you feel really old), ten and a half years before Windows XP was released was April 1991, when Windows 3.0 was Microsoft's reigning operating system. Windows NT wouldn't be released for another two years. XP's been with us for an eternity, in computer terms.
It may not be quite fair to call Windows XP a "decade-old operating system" -- it was after all the top of the line until Windows Vista was released, though even that was five years ago. Still, with such an impressively large installed base, it's a good bet that an article like this one written five or ten years from now will include "ancient x86 box running Windows XP" in its rogues gallery.