The U.S. Space Shuttle computers cannot tell one year from another.
Some of the software, when it hits December 31st, goes on to December 32nd (or,
day 366). This is why the Shuttle can never operate through a change of year.
The Shuttle control computers on earth do recognize the changing of the year,
but some of the computers on the Shuttle do not, which makes News Years Eve
flights impossible. The Shuttle is reaching the end of its useful life, and
that three decade old software bug is one of many ways it is showing its age.
The Shuttle was designed in the late 1970s, and many of the computers are still
using 1980s computer technology. The web, and sites like eBay, have been a
salvation for the Shuttle. That's because these auction sites make available a
lot of ancient (1980s) computer technology, to provide spares for Shuttle gear
that is no longer manufactured.
Shuttle is going to be in use for another four years, and despite a budget of
over $3 billion a year, it's not a sure thing that all the ancient computers,
and their software, on the Shuttles will be updated. This is a problem common
with many military systems that have been in use for decades. These older systems
also depend on spare parts via eBay, to keep them operational.
ancient gear is not unique to the military. There are many commercial firms
that also keep computers and machinery operational that, to most of us, appear
ancient. The attitude is, if the stuff does the job, then keep it around. Works
for the space program and military as well. As the old saying goes, if it ain't
broke, don't fix it. But it does seem odd at times.