[time-nuts] Re: UTC - A Cautionary Tale

Brooke Clarke brooke at pacific.net
Thu Jul 14 12:03:36 EDT 2005

Hi David:

My concern is that if the time between leaps gets to be long then there 
will be another Y2K type problem.  I.e. programmers will ignore the Leap 
Hour, figuring that they will be dead when it occurs, and when it does 
there will be many broken programs.

The GPS time scale does not have leap seconds.  Would it be suitable for 
those applications where leap seconds are a problem?

Have Fun,

Brooke Clarke, N6GCE
w/Java http://www.PRC68.com
w/o Java http://www.pacificsites.com/~brooke/PRC68COM.shtml

David Forbes wrote:

> At 11:13 PM -0700 7/13/05, Rob Seaman wrote:
>> Howdy,
>>>  This is a little missive from an astronomer on the delicate subject 
>>> of the divergence of UTC from UTx. It seems that those bastards in 
>>> the precision timing community want to abandon UTC's leap seconds 
>>> entirely because they are too much trouble, and he's hopping mad.
>> Note that my message was composed for astronomers, not you guys.
>> Several of us in the astronomical software community have been 
>> following this issue since before Y2K:
>>     http://www.ucolick.org/~sla/leapsecs
>> We are as "hopping mad" about the sneaky process as about the 
>> proposal.  Note our two tiered objection:  they not only propose to 
>> cease issuing leap seconds, they propose to continue calling the 
>> resulting time scale "Coordinated Universal Time".  There are many 
>> flavors of UT - UTC should not be divorced from the others.  Call a 
>> leap second-less civil time anything you want - simply don't call it 
>> "UTC".
> I agree that important processes should not be sneaky, but they often 
> are. Manhattan Project, anyone?
>>>  [His most amusing argument against modifying UTC is that astronomy 
>>> software tends to use UTC not UT1 etc.]
>> Amusing how?
> It's amusing in that UTC is civil time, not astronomical time, which one 
> would expect astronomers to use. I didn't say it's bad or wrong, just 
> that it's amusing. Jokes are amusing. I have a sense of humor, which 
> many people seem to lose when their favorite ideas are attacked.
>> Also note that UT1 is only available after the fact.  UTC is a 
>> deterministic (if segmented) timescale which provides not only an 
>> approximation (and prediction) of UT1, but also provides access to TAI 
>> two or three orders of magnitude more precisely yet.  It may not be 
>> perfect, but then - this proposal isn't designed to provide something 
>> better.  Imagine what might have been achieved if the precision timing 
>> community had spent the seven year leap second hiatus working to 
>> improve UTC rather than to sabotage it.
> UTC is NOT deterministic. It has leap seconds inserted randomly with 
> only 6 months advance notice. You can't plan a mission to Saturn based 
> on UTC.
> There was a big discussion about this subject on the time-nuts list a 
> couple weeks ago precisely *because* UTC is not deterministic. Computer 
> programmers have to stand on their heads to design systems to calculate 
> future time using UTC.
>> I find it surreal that it is the precision timing community who are 
>> arguing that the public have no need for access to precision time.
> The time the public uses doesn't need to be locked to the Earth's 
> rotation to within a second over the short term. The thing to solve is 
> the long-term drift, which can be predicted far in advance, but not to 
> within a second a year.
> I propose a better solution that will keep the civil timescale locked to 
> the Earth's rotation to within a minute and be deterministic for 
> hundreds of years in advance: Create leap minutes and *define them in 
> advance* for the next 500 years (or however far in advance is practical) 
> based on the second-order curve of the known characteristics of the 
> Earth's rotation. Then the programmers will have an algorithm to 
> guarantee that their clock code will work until long after they're dead.
>> Rob Seaman
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