"Time Warp"

Graham Klyne gk at ninebynine.org
Thu Dec 4 10:30:59 EST 2003

I spotted this and thought of some recent(ish) discussions...

# "Time Warp"
New Scientist (11/22/03) Vol. 180, No. 2422, P. 30; Battersby, Stephen

An unusual practice of modern timekeeping is the insertion of a "leap 
second" into the calendar, which occurs less than once a year on average; 
this is done to make up for the discrepancy between international atomic 
time and solar time, which is changing as the Earth's rate of rotation 
gradually slows. Since the inception of leap seconds 30 years ago, 
coordinated universal time has lagged in fits and starts behind universal 
atomic time, and the situation has been complicated by the rollout of 
various technologies that have their own internal time frames. "With [these 
technologies] becoming more interactive, they need to be synchronized," 
states the Naval Research Laboratory's Ron Beard. Technologies ranging from 
GPS to air traffic control systems to the Internet to military systems are 
not designed with leap seconds in mind, which makes leap second insertion 
the responsibility of software engineers. This task is difficult enough, 
but complicating matters is the unpredictable nature of the Earth's slowing 
spin, a phenomenon attributed to as-yet-indeterminate internal forces; in 
fact, the planet's rotation has recently sped up, the result being no leap 
seconds for the last five years. Affected by this is Motorola's Oncore GPS 
receiver, which will add an extra day to the calendar just after midnight 
on the morning of Nov. 28, 2003. This extra day will only last for a 
second, but Motorola GPS product manager Dave Huntingford is worried that 
this could affect Nov. 28 cell phone bills and lead to lost revenues; 
Global Timing Services consultant William Klepczynski is even more 
concerned that such glitches, when combined with worker stress, could lead 
to disastrous errors in air traffic control. Beard and others think leap 
seconds should be jettisoned in favor of a continuous timekeeping system 
called international time, although astronomers fervently oppose this 
because of their high reliance on software that automates the alignment of 
their telescopes.
-- http://www.acm.org/technews/articles/2003-5/1203w.html#item17

Graham Klyne
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