[LEAPSECS] Standards of time zones -Brooks Harris

[Warner Losh]

http://www.youtube.com/watch?v=-5wpm-gesOY is required viewing.

Warner

On Jan 7, 2014, at 4:22 PM, Brooks Harris wrote:


> Hi,

> 

> First, this is my first posting to your list, forgive me if the subject has been covered.

> 

> Second, I am a colleague Stephen Scott, also a new subscriber who posted a question earlier this week - (Subject: Local insertion of leap seconds).

> 

> My question is about the current state of standards concerning time zones.

> 

> Steve Allen's "Time Scales" http://www.ucolick.org/~sla/leapsecs/timescales.html <http://www.ucolick.org/%7Esla/leapsecs/timescales.html> is a tremendous help in many regards, and my thanks and appreciation for the work collected there. But it seems to side-step explanation of time zones, and its here I'm asking for guidance.

> 

> I fully understand time zone specifications are fractured. My objective is to determine what standards are most relevant currently, that is, what standards may be considered "in force". And where none exist, to state some sort of rules of "common use" or "common practice" without referring to the impossibly large collection of local jurisdictions and laws.

> 

> In particular -

> 

> A) "International Date Line", which is probably not standardized except by local decree, but the "180 degrees from the Greenwich meridian" has provenance back to the "International Meridian Conference of 1884" (not its proper name). Is there more modern standard that codifies this in any way?

> 

> B) The "International Meridian Conference of 1884" contains significant discussion of the idea "That these standard meridians should continue to be designated as even multiples of fifteen degrees from Greenwich", but there appears to be no explicit resolution of vote on the topic. I am unable to pick up the trail from there. There are many references in other conferences preceding and after the 1984 conference, but I have not discovered any official action on the subject. Again, is there any modern standard regarding that issue?

> 

> ISO 8601 describes using "offset from UTC" to indicate "time zone", but as far as I can tell it does not state either what a "time zone" may be or why an offset to a "time zone" from UTC might be useful. Is there any other standard that might describe this relation of UTC (zulu) to the "time zone" or "local time" more rigorously?

> 

> Of course the definition of "Greenwich meridian" has undergone many refinements and name changes since 1884. Claude Boucher describes the state of Formal international recognition of the International Terrestrial Reference System (ITRS)

> 

> https://www.google.com/#q=Formal+international+recognition+of+the+International+Terrestrial+Reference+System+(ITRS). 

> 

> Are there descriptions of "time zones" amongst the standards in this field?

> 

> And, of course, there is the subject of "Daylight Savings", apparently begun by George Vernon Hudson. Are there any modern standards or implementation guidance documents in force?

> 

> I'm aware of tz databse, of course, but here too there seems to be lack of clarity about what rules are being implemented, or, at least, I've found no consolidated statements of those rules there.

> 

> Comments and guidence welcomed, thanks very much,

> 

> -Brooks Harris

> 

> 

> 

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