Conscientious sysadmins face a dilemma on December 31, when a new leap second will threaten the stability of computer systems and networks.
Scientists occasionally add a leap second to Coordinated Universal Time (UTC), the time reference most clocks are set by, so as to keep it in step with the earth’s gradually slowing rotation. If they didn’t, then clocks would be off by about a minute at midday by 2100.
Computer systems don’t like leap seconds as they are programmed to expect the same number of seconds in every minute of every hour of every day. The various ways of tricking them into accepting the extra second — stretching out all the other seconds in the preceding minute, hour or day, repeating the same second twice, or creating a 61st second in a minute, can cause chaos as they affect different computers in different ways.
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