The existing public-domain time zone stuff lets you know how to represent local time if you provide the identity of the set of rules that apply. Recent mail has dealt with the matter of handling things such as geographic locations or phone system area codes. My sense is that layered software is the way to go. The bottom level turns a time-zone identifier into a representation of the rules that apply. Built on top of this are packages that take different forms of input (phone system area code, geographic location) and deliver up time-zone identifiers. The existing time-zone stuff is a bottom level. And there might be multiple higher levels--for example: topmost geographic location to phone system area code middle phone system area code to time zone identifier bottom time-zone identifier to rules that apply The organization of the higher levels would, of course, be immaterial to what goes on at the bottom level. A consideration in determining the time-zone identifiers to use in such a setup is the independent usability of the bottom level. The existing time zone stuff uses identifiers of the form big-geographic-region/city; this allows some meaningful applications (such as setting the local time to be used on a computer) without recourse to a higher level (proof by existence). There are other considerations as well (technological, political, technological, astrological...). And determining what to use as a time-zone identifier ought not be done in a vacuum: if the same identifier can be used for other purposes, we've simplified our lives.
Date: Fri, 16 Feb 2001 15:47:48 -0500 From: "Olson, Arthur David (NCI)" <olsona@dc37a.nci.nih.gov> Message-ID: <4E0F9DDCA724D411B2120008C75DB71DD0F593@nihexchange2.nih.gov> I agree with the generality of what you say, but unfortunately ... | topmost geographic location to phone system area code | middle phone system area code to time zone identifier that particular layering won't work. As well as regularly altering its time zone rules, Australia also just recently altered all its phone system area codes. Now we have just 4 area codes for the country. Anyone following this discussion will know that we have more than 4 timezones (using the tzdata definition of a timezone anyway). Eg: South Aus, NT, and West Aus are all the same phone area code, but are three different timezones. Vic and Tas the same. NSW and (I think) Lord Howe Island the same (I'm not certain what area code LHI uses, but I think it will be the same as NSW). If Qld ever decides to do the rational thing and introduce summer time in its south east corner (one part of Aus, along with north east NSW of course) where it really would be useful, then that would be another. Now if you extended the phone system identifier to include the exchange prefix, things have a better chance at working, but now you have a nightmare of administration (as those things spring up new almost daily). And even then, there's no guarantees - phone numbers are allocated to suit the requirements of the phone system (and to a lesser degree, its users...) any relationship with timezones is purely accidental. The relationship really needs to be directly from gegraphical location (perhaps postal area code, or zip code - those are usually small enough so they will probably be within a timezone - though even there, they are assigned to suit the post office, not the sun) to timezone, and from the same thing to phone area code (if that is needed). kre
participants (2)
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Olson, Arthur David (NCI) -
Robert Elz