[LEAPSECS] happy anniversary pips

[Warner Losh]

On Feb 10, 2014, at 4:24 PM, Rob Seaman wrote:


> On Feb 10, 2014, at 9:57 AM, Warner Losh <imp at bsdimp.com> wrote:

> 

>> On Feb 10, 2014, at 9:02 AM, Rob Seaman wrote:

>> 

>>> Like I said, it is an attempt to confuse two different concepts.

>> 

>> We disagree here then. Atomic time is adequate for civil needs. The small divergence can be handled the same way we handle differences in time between the sun and the UT time now: time zones.

> 

> There hasn’t been the slightest investment of systems engineering in evaluating this notion of hiding variations in length of day in the timezone system.  We had a cat once that liked to hide squirrel parts under the doormat.  This is like that.

> 

> Note also that Tom Scott’s rant is titled “The Problem with Time & Timezones”:

> 

> 	http://youtu.be/-5wpm-gesOY

> 

> Leap seconds are just a relish added at the end.  He clearly doesn’t perceive timezones as a solution, but rather as part of the problem.


The leap forward or back an hour due to increasing out-of-syncness with the sun would be a drop in the bucket.


>> These times zones would move on a scale of multiple decades or centuries.

> 

> It’s almost as if the last decade-plus of discussions never happened.  Just continue to make the same empty unsupported assertion that doesn’t actually appear anywhere in the ITU proposal.  Please see many previous messages on this topic.  Here I’ll just note that these local updates would be clustered into extended periods of great confusion.  This isn’t an issue of two dozen timezones, but rather of the thousands of local jurisdictions that would be choosing what timezone to adhere to.  Some would toggle back-and-forth for decades during these transitional centuries as different political parties take power.


Pure speculation on your part. And also irrelevant. These are sovereign states.


>> This would suffice to keep the clocks on the wall aligned to the sun in the sky to the same error as we have today.

> 

> This confuses the reporting of local time with the maintenance of the underlying global timescale.  Future historians would curse our names for introducing vast uncertainty into future chronologies.  Predictions of future events (say, solar eclipses) would be unable to engage with a local time that might differ +/- one hour rather than a few seconds.


The same problem exists with leap seconds... 


> Equating this with daylight saving time is a particular red herring since only a small fraction of world participates in any of the variations of DST, but also since these changes wouldn’t be matched by a seasonal readjustment half a year later.  Each locality would be applying leverage to their particular timezone, but the timezone as a whole would have fuzzy edges, perhaps extending all the way through to the next era of confusion.


I engaged in no such red herring.


>> It moves the alignment from one part of the system to the other. It doesn't confuse any concepts at all, but rather properly applies them to an alternative solution.

> 

> It certainly confuses the concepts that describe the actual physical situation.  And instead of keeping track of a single monotonic list of leap seconds, all software would have to track vast numbers of worldwide lists of local timezone peccadillos.  A single Olson tz database might no longer suffice since it would have to be normalized against individual tables for cities and counties, let alone countries and continents.  And pray, what happens in such a situation to the concepts of the prime meridian and the international date line?  I presume we’re to assume they stay put?  Why should they?


It does not confuse anything. And you overstate the effects relative to other timezone effects. The timezone decisions would be made on a national level, just like they are today. Salt Lake City and Denver are on the same time, even though the sun sets half an hour later in SLC.


> And for that matter I’m skeptical that it doesn’t confuse those few concepts you appear to care about.  You’d be requiring a complex tz schema (much more complex than currently) be added to many classes of software that simply get by with ambient UTC now.


How so. I don't understand this at all. You add an hour or not after the difference gets large enough to care, and that process operates on a time scale of decades or centuries.


>> I get that people don't like this, and that there's some resistance to it on aesthetic grounds dressed up in the guise of technical arguments about universal not meaning what it has always meant, and that entrenched interests aren't unhappy enough with the status quo to risk changes...

> 

> 

> Oh, if only I could lay claim to being an entrenched aesthete :-)

> 

> You don’t like arguments about Universal Time needing to continue to denote the same term of art it always has?  ISO disagreed with you enough to send a technical committee chair from Hong Kong to Washington, DC:

> 

> 	http://www.cacr.caltech.edu/futureofutc/aas223/presentations/2-1-ISOterminologyAAS.pdf

> 

> Before it is used as implicit justification for redefining time policies worldwide, the ITU really ought to back it up with something more than “Hey, that sounds plausible!"


Also irrelevant. I said Atomic Time can be the basis for Civil time. Universal Time never entered into it, other than being displaced as the basis for Civil Time. It would exist, unchanged, like it has existed in all its various flavors. As the understanding of time has increased, we've gone from local time to UT to a plethera of UT (UT0, UT1, UT2) as well as UTC. Apart from some naming issues with the new Atomic Time (which you bogusly bring up here: I made no such assertions about the name of the new Atomic Time), Universal time would continue. Newcomb's equations would still be useful, and you'd just have a new difference between UTx and Atomic time. These numbers could easily be published for people getting only an Atomic Time stream who need to know the delta from UTx, and systems could be written to emulate the current broadcast of UTC if systems need to be fed with that info directly.

My basic argument is that we can coordinate on atomic time, base civil time on that and synchronize to the sun with an offset to the time zones that sovereign states use today to determine what they want their people to use.

Warner