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NEWS BLOG by Tony Flanders
Time Committee Procrastinates
The International Telecommunication Union, an arm of the United Nations, recently announced with great fanfare that it intended to settle the "problem" of leap seconds once and for all. At their meeting on January 19th, the committee decided to kick the decision down the road for another three years. Procrastination — what could be more appropriate for an official international committee on time?
Truth be told, this choice was as good as any other. Leap seconds have been added periodically to keep the official time in sync with Earth's uneven, unpredictable rotation, most recently at the beginning of 2009.
These leap seconds upset techies, because they mean that the internal clocks inside devices can't run autonomously. Instead, somebody has to go in there every few years and set the clock back a second. So people who run computer networks would be much happier if leap seconds were abolished.
However, abolishing leap seconds would just kick the problem down the road for a millennium or two, by which time local noon (the Sun being at its highest) would occur several hours late. People seem (strangely enough) to be willing to put up with daylight saving time, but I doubt anybody would be happy having the Sun highest at 11 p.m.!
What's my opinion? It's a thorny problem without any good long-term solution. But I object on principle to bending people's behavior to suit the convenience of computer techies. Machines were meant to serve us, not the other way around!
For more information, see our online article on time.
Truth be told, this choice was as good as any other. Leap seconds have been added periodically to keep the official time in sync with Earth's uneven, unpredictable rotation, most recently at the beginning of 2009.
Precision time, then and now: an antique chronometer and modern atomic clock at the U.S. Naval Observatory in Washington, D.C.
U.S. Naval Observatory
However, abolishing leap seconds would just kick the problem down the road for a millennium or two, by which time local noon (the Sun being at its highest) would occur several hours late. People seem (strangely enough) to be willing to put up with daylight saving time, but I doubt anybody would be happy having the Sun highest at 11 p.m.!
What's my opinion? It's a thorny problem without any good long-term solution. But I object on principle to bending people's behavior to suit the convenience of computer techies. Machines were meant to serve us, not the other way around!
For more information, see our online article on time.
Posted by Tony Flanders, January 27, 2012
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First comments (from 17)
Time sync
Posted by Sandy Brown
January 27, 2012 At 10:12 AM PST
"...people who run computer networks..." Funny, but my computer is connected to the Internet, and its time is automatically updated via the NIST tie service. Since they run the "atomic clock," where's the problem???
Non-networked devices are the real challenge
Posted by Brooks Davis
January 27, 2012 At 11:14 AM PST
I have no idea where the canard that network devices are the problem came from, but that mostly isn't the case. The Network Time Protocol (NTP) can deal with leap seconds though not all time sources keep their list of leap seconds up to date. The more significant issues lie elsewhere.
One issue is that you can not build a practical non-networked device (including a device with GPS clock) that will definitely display the correct UTC wall clock time at +31536000 seconds. The problem is that there are up to 4 opportunities to change that value during a given year as determined by the International Earth Rotation and Reference Systems Service.
Another issue is that it is often useful to have a continuous time scale for precision logging and it is further useful if that time scale aligns with wall clock time. With leap seconds, neither is true.
As the worry about precession of wall time relative to solar time in the indefinite future; we already have a solution: timezones. As solar noon drifts too far outside the timezone we can make a periodic change. At the current rate of change in the speed of earth's rotation the general public will not even notice for several centuries unless they try to sync their cellphone and high precision sundial. By making a large jump and planning for it well in advance we will be able to keep solar time acceptably aligned with wall clock time while allowing reasonably long lived devices to operate without needless updates.
correction to previous post
Posted by Brooks Davis
January 27, 2012 At 11:26 AM PST
GPS time does not include leap seconds, but the GPS signal does include a mechanism for dealing with leap seconds by using the week number (WN) field. This page discusses some of the issues with doing so: http://www.colorado.edu/geography/gcraft/notes/gps/gpseow.htm
All Hail Our Mechanical Overloards!
Posted by jeff wahlgren
January 27, 2012 At 01:12 PM PST
"Machines were meant to serve us, not the other way around!"
And yet most of my day is spent on 'work-arounds' for the special cases my machines cannot accomodate.
The future of UTC
Posted by Rob Seaman
January 27, 2012 At 02:17 PM PST
For additional information and a somewhat different point of view, see http://futureofutc.org
Decisions, decisions
Posted by Anton Szautner
January 27, 2012 At 04:28 PM PST
Now THAT was funny!
Thanks for the good laugh.
Leap seconds and time
Posted by Frank Reed
January 27, 2012 At 05:03 PM PST
I'm a Time Lord. No really. It was announced on the radio so it must be true. And so is Rob Seaman (see above post). You can listen to many minutes of Rob and a couple of minutes of me here: http://www.startalkradio.net/?p=323.
As a Time Lord (Ha!), I can assure you that this isn't just a matter of the time of Nature versus the time of Machines. Atomic Time and GPS Time and the astronomers' Ephemeris Time (in its many acronymed names) are realizations of a time that is more absolute, more fundamentally-founded in the laws of physics than the UTC that we use today. They are "Physics Time" as opposed to "Earth Rotation Time". The latter is the principle underlying UT, and is based on one very large but slightly wobbly artifact: the Earth itself.
Time Zones
Posted by KC
January 27, 2012 At 06:22 PM PST
As far as allowing time to drift so that eventually we have to shift time zones doesn't sound like a good idea. People are often 'time-zone centric'...the major population centers tend to be near the center of the time zone and so people forget about the folks living at the edges. For them they are already putting up with unpleasant disconnects with solar time. If you don't make small adjustments, then people will have to put up with increasingly unpleasant conditions for centuries.
Time Zones
Posted by Frank Reed
January 28, 2012 At 04:46 AM PST
KC, you wrote: "the major population centers tend to be near the center of the time zone and so people forget about the folks living at the edges" .... But it's not true at all. Time zones have been drifting east since they were first created. And since "Daylight Saving Time" in many countries, especially the US, is not in effect for most of the year, we are FAR from solar time and 'major population centers' are no longer even close to the appropriate mean time. Just consider the eastern US. For nearly two-thirds of the year, cities from Boston at the eastern end all the way over to Detroit and Toledo and Indianapolis use a mean time which corresponds to 60 degrees west longitude as far as the actual longitude of the Sun is concerned. Get out a globe (virtual or otherwise) and consider what this means: when a clock in Detroit says 12:00:00 noon, the Sun is over a meridian far out in the Atlantic well east of Bermuda, east of most of Nova Scotia, and even east of Martinique in the Lesser Antilles. We do not keep time by the Sun.
Time Zones
Posted by Frank Reed
January 28, 2012 At 04:56 AM PST
Further on shifting time zones. It's an easy solution well within the normal rules of "mean time" law as it already exists. Consider Michigan. That state has legislated itself onto Eastern (US) Time since the middle of the 20th century. By geography and longitude rules, they ought to be in Central Time but convenience and culture have persuaded them to live on Eastern Time. They can switch "back" to Central Time if they wish at any time. In 200 years, if the slow drift implied by dropping leap seconds were to become impractical, they could easily legislate themselves back to Central Time. It's almost easier to imagine that law change than it is to imagine Michigan as an autonomous entity in 200 years. And yet there's still a catch. Time zone shifting cannot stop the movement of the date. Without global agreement, the beginning of the calendar day would slowly drift east. Eventually there would even be confusion over the day of the week. Is it Sunday yet? Would there be any fraction of the population in 500 years who would be concerned over whether the calendar date is really Saturday or Sunday??
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comments (17)