A number of people have noticed their system clocks being advanced by 100
years. This can cause a number of problems because most software compiled with
Microsoft Visual C will not work after the year 2037 (a problem similar in some
ways to the 'year 2000 problem'). Email software is particularly prone to
failure if the system clock is advanced 100 years for example.
At the time of writing, there are no known viruses which have this effect.
However, there are some viruses which mark infected files by advancing their
creation/modification date by 100 years. There is also one known virus which
changes the system date - on infection Winword/Mess changes it to either 26th
July 1995 (under Word 8) or 31st March 1994.
The most likely cause of this problem is a bug in the computer's BIOS. There
is a known bug in early Pentium BIOSes by Phoenix for example, and this has
been carried through into BIOSes based on the Pheonix code such as those used
in some Compaq machines. This bug means that if a machine is left running over
midnight (i.e. when the date changes), and a specific mechanism for calling the
date is subsequently used, the date advancing code in the BIOS erroneously
increments the centuries field of the system clock. This generally seems more
likely to occur around the end of the month, although it may take a few days
for the user to notice the change.
If the BIOS is the cause, it should not cause more than the occasional minor
nuisance because the system clock can be reset to the correct date by the user.
Compaq have issued a flash BIOS upgrade to deal with the problem, and other
manufacturers may also provide upgrades.