Picture yourself riding an elevator in a tall office building, when the clock strikes midnight. The elevator controller has its time synced via posix time. The controller schedules when to stop running the elevator motor by reckoning from its last known position and projecting forward according to its estimated speed. Normally this calculation is performed 10 times a second so it's a smooth transition.
But when the clock jumps back abruptly by 1.0 s, the controller gets confused. Its next control loop update cycle is now scheduled 1100 ms into the future instead of the normal 100 ms period. This delays the motor shutdown signal and even causes the controller to miss the top-of-position sensor. The elevator car slams into the roof of the building. The cable snaps and all passengers contemplate Einstein for 10 s as the elevator car freefalls to their certain doom.
Well they would have, except that cable elevators have had mechanical safeties for a backup system since the 19th century.
OK, so instead:
Picture yourself receiving life-saving radiation therapy, when the clock strikes midnight ...
But when the clock jumps back abruptly by 1.0 s, the controller gets confused. Its next control loop update cycle is now scheduled 1100 ms into the future instead of the normal 100 ms period. This delays the motor shutdown signal and even causes the controller to miss the top-of-position sensor. The elevator car slams into the roof of the building. The cable snaps and all passengers contemplate Einstein for 10 s as the elevator car freefalls to their certain doom.
Well they would have, except that cable elevators have had mechanical safeties for a backup system since the 19th century.
OK, so instead:
Picture yourself receiving life-saving radiation therapy, when the clock strikes midnight ...