practice

DoI: 10.1145/1941487.1941505

Article development led by queue.acm.org

Finding a lasting solution to the leap seconds
problem has become increasingly urgent.
BY PouL-hennInG KamP
the one-
second
War

thanks to a secretive conspiracy working mostly below the public radar, your time of death may be a minute later than presently expected. But don’t expect to live any longer, unless you happen to be responsible for time synchronization in a large network of computers, in which case this coup will lower your stress level a bit every other year or so.

We’re talking about the abolishment of leap seconds, a crude hack added 40 years ago to paper over the fact that planets make lousy clocks compared with quantum mechanical phenomena.

Timekeeping used to be astronomers’ work, and the trouble it caused was very academic. To the rural

population, sunrise, midday, and sunset were plenty precise for all relevant purposes.

Timekeeping became a problem for non-astronomers only when ships started to navigate where they could not see land. Finding your latitude is easy: measure the height of the midday sun over the horizon, look at the table in your almanac, done. Finding your longitude is possible only if you know the time of day precisely, and the sun will not tell you that unless you know your longitude.

If you know your longitude, however, the sun will tell you the time very precisely. Using that time, you can make tables of other nonsolar astronomical events—for example, the transits of the