"Time Warp"

Seth Kurtzberg seth at cql.com
Fri Dec 5 12:27:21 EST 2003

This is a very common practice.  I've worked on several satellite 
projects and they all use leap seconds from time to time.

There are accepted ways in code to handle leap seconds.  If anyone 
needs details I can provide them.

On Dec 4, 2003, at 3:30 AM, Graham Klyne wrote:

> 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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Seth Kurtzberg
ISEC Research and Network Operations Center
seth at isec.us

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