time bomb

time bomb n.  A subspecies of {logic bomb} that is
   triggered by reaching some preset time, either once or
   periodically.  There are numerous legends about time bombs set up
   by programmers in their employers' machines, to go off if the
   programmer is fired or laid off and is not present to perform the
   appropriate suppressing action periodically.

   Interestingly, the only such incident for which we have been
   pointed to documentary evidence took place in the Soviet Union in
   1986!  A disgruntled programmer at the Volga Automobile Plant
   (where the Fiat clones called Ladas were manufactured) planted a
   time bomb which, a week after he'd left on vacation, stopped the
   entire main assembly line for a day.  The case attracted lots of
   attention in the Soviet Union because it was the first cracking
   case to make it to court there.  The perpetrator got a suspended
   sentence of 3 years in jail and was barred from future work as a
   programmer.